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Page 1A Helpful Hand
DEPARTMENT OF COMPUTER SCIENCE
AND ENGINEERING
OBJECT ORIENTED PROGRAMMING:
OOP Concepts:
The object oriented paradigm is built on the foundation laid by the structured programming concepts. The fundamental change in OOP is that a program is designed around the data being operated upon rather upon the operations themselves. Data and its functions are encapsulated into a single entity.OOP facilitates creating reusable code that can eventually save a lot of work. A feature called polymorphism permits to create multiple definitions for operators and functions. Another feature called inheritance permits to derive new classes from old ones. OOP introduces many new ideas and involves a different approach to programming than the procedural programming.
Benefits of object oriented programming:
Data security is enforced. Inheritance saves time.
User defined data types can be easily constructed. Inheritance emphasizes inventions of new data types.
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Page 3Large complexity in the software development cn be easily managed.
Basic C++ Knowledge:
C++ began its life in Bell Labs, where Bjarne Stroustrup developed the language in the early 1980s. C++ is a powerful and flexible programming language. Thus, with minor exceptions, C++ is a superset of the C Programming language.
The principal enhancement being the object –oriented concept of a class. A Class is a user defined type that encapsulates many important mechanisms. Classes enable programmers to break an application up into small, manageable pieces, or objects.
Basic concepts of Object oriented programming:
Object:
Objects are the basic run time entities in an object-oriented system.
thy may represent a person, a place, a bank account, a table of data or any item that the program has to handle.
Class:
The entire set of data and code of an object can be made of a user defined data type with the help of a class.
I fact, Objects are variables of the type class.
Once a class has been defined, we can create any number of objects belonging to that class
A class is thus a collection of objects of similar type.
for example: mango, apple, and orange are members of the class fruit. ex: fruit mango; will create an object mango belonging to the class fruit.
Data Abstraction and Encapsulation:
The wrapping up of data and functions in to a single unit is known as encapsulation.
Data encapsulation is the most striking feature of a class.
The data is not accessible to the outside world, and only those functions which are wrapped in the class can access.
This insulation of the data from direct access by the program is called data hiding.
Abstraction :
Abstraction referes to the act of representing essential features without including the background details or explanations.
since the classes use the concept of data abstraction ,thy are known as abstraction data type(ADT).
Inheritance :
Inheritance is the process by which objects of one class acquire the properties of objects of another class. Inheritance supports the concept of
hierarchical classification. for example:
The bird 'robin ' is a part of the class 'flying bird' which is agian a part of the class 'bird'. The concept of inheritance provide the idea of reusability.
Bird Attributes: Feathers Lay eggs Flying bird Attributes: --- --- Non flying bird Attributes: --- --- Robin Attributes: _________ Swallow Attributes: _________ Penguin Attributes: _________ Kiwi Attributes: _________
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Page 5POLYMORPHISM:
Polymorphism is another important oop concept. Polymorphism means the ability to take more than one form. an operation may exhibit different instances. The behavior depends upon the types of data used in the operation.
The process of making an operator to exhibit different behaviors in different instance is known as operator overloading.
Polymorphism plays an important role in allowing objects having different internal structures to share the same external interface. Polymorphism is extensively used if implementing inheritance.
The Object-Oriented Approach
The fundamental idea behind object-oriented languages is to combine into a single program entity both data and the functions that operate on that data. Such an entity is called an object.
An object's functions, called member functions in C++ (because they belong to a particular class of objects), typically provide the only way to access its data. If you want to read a data item in an object, you call a member function in the object. It will read the item and return the value to you. You can't access the data directly. The data is hidden, so it is safe from accidental alteration. Data and its functions are said to be encapsulated into a single entity. Encapsulation and data hiding are key terms in the description of object-oriented languages.
Shape Draw() Circle Object Draw() Box Object Draw() Triangle Object Draw()
Java History:
Java is a general-purpose; object oriented programming language developed by Sun Microsystems of USA in 1991. Originally called “oak” by James Gosling, one of the inventors if the language. This goal had a strong impact on the development team to make the language simple, portable, highly reliable and powerful language.
Java also adds some new features. While C++ is a superset of C. Java is neither a superset nor a subset of C or C++.
C++
C
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Page 7Process of building and running java application programs:
The way these tools are applied to build and run application programs is create a program. We need create a source code file using a text editor. The source code is then compiled using the java compiler javac and executed using the java interpreter java. The java debugger jdb is used to find errors. A complied java program can be converted into a source code.
Text Editor Java Source Code Javadoc HTML files Javac Java Class File Javah Header Files
Java (only file name) Jdb (database)
Java program Output
JAVA PROGRAMMING LAB PROGRAMS LIST
1. Write a Java program that prints all real solutions to the quadratic equation ax2+bx+c = 0. Read in a, b, c and use the quadratic formula. If the discriminant b2-4ac is negative, display a message stating that there are no real solutions. 2. The Fibonacci sequence is defined by the following rule. The first 2 values in
the sequence are 1, 1. Every subsequent value is the sum of the 2 values preceding it. Write a Java program that uses both recursive and non-recursive functions to print the nth value of the Fibonacci sequence.
3. WAJP that prompts the user for an integer and then prints out all the prime numbers up to that Integer.
4. WAJP that checks whether a given string is a palindrome or not. Ex: MADAM is a palindrome.
5. WAJP for sorting a given list of names in ascending order. 6. WAJP to multiply two given matrices.
7. WAJP that reads a line of integers and then displays each integer and the sum of all integers. (use StringTokenizer class)
8. WAJP that reads on file name from the user, then displays information about whether the file exists, whether the file is readable, whether the file is writable, the type of file and the length of the file in bytes.
9. WAJP that reads a file and displays the file on the screen, with a line number before each line.
10. WAJP that displays the number of characters, lines and words in a text. 11. WAJP that:
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Page 9(b) Converts Infix expression to Postfix expression (c) Evaluates a Postfix expression
12. Write an Applet that displays a simple message.
13. Write an Applet that computes the payment of a loan based on the amount of the loan, the interest rate and the number of months. It takes one parameter from the browser: Monthly rate; if true, the interest rate is per month, otherwise the interest rate is annual.
14. WAJP that works as a simple calculator. Use a grid layout to arrange buttons for the digits and for the + - x / % operations. Add a text field to display the result.
15. WAJP for handling mouse events. 16. WAJP for creating multiple threads.
17. WAJP that correctly implements Producer-Consumer problem using the concept of Inter Thread Communication.
18. WAJP that lets users create Pie charts. Design your own user interface (with Swings & AWT).
19. WAJP that allows user to draw lines, rectangles and ovals.
20. WAJP that implements a simple client/server application. The client sends data to a server. The server receives the data, uses it to produce a result and then sends the result back to the client. The client displays the result on the console. For ex: The data sent from the client is the radius of a circle and the result produced by the server is the area of the circle.
21. WAJP that illustrates how runtime polymorphism is achieved.
22. WAJP to generate a set of random numbers. Find its sum and average. The program should also display ‘*’ based on the random numbers generated. 23. WAJP to create an abstract class named Shape, that contains an empty method
Hexagon, such that each one of the classes contains only the method
numberOfSides(), that contains the number of sides in the given geometrical figure.
24. WAJP to implement a Queue, using user defined Exception Handling (also make use of throw, throws).
25. WAJP that creates 3 threads by extending Thread class. First thread displays “Good Morning” every 1 sec, the second thread displays “Hello” every 2 seconds and the third displays “Welcome” every 3 seconds. (Repeat the same by implementing Runnable)
26. WAJP that will compute the following series: (a) 1 + 1/2 + 1/3+ …….+ 1/n
(b) 1 + 1/2 + 1/ 22 + 1/ 23 + … … + 1/ 2n (c) ex = 1 + x/1! + x2/2! + x3/3! + … …
27. WAJP to do the following:
(a) To output the question “Who is the inventor of Java?” (b) To accept an answer
(c) To printout “GOOD” and then stop if the answer is correct (d) To output the message “TRY AGAIN”, if the answer is wrong
(e) To display the correct answer, when the answer is wrong even at the third attempt
28. WAJP to transpose a matrix using ‘arraycopy’ command.
29. Create an inheritance hierarchy of Rodent, Mouse, Gerbil, Hamster etc. In the base class provide methods that are common to all Rodents and override these in the derived classes to perform different behaviors, depending on the specific type of Rodent. Create an array of Rodent, fill it with different specific types of Rodents and call your base class methods.
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Page 11Program Statement :
Write a Java program that prints all real solutions to the quadratic equation ax2+bx+c = 0. Read in a, b, c and use the quadratic formula. If the discriminant b2-4ac is negative, display a message stating that there are no real solutions. Program :
import java.io.*; class Quadratic {
public static void main(String args[])throws IOException {
double x1,x2,disc,a,b,c;
InputStreamReader obj=new InputStreamReader(System.in); BufferedReader br=new BufferedReader(obj);
System.out.println("enter a,b,c values"); a=Double.parseDouble(br.readLine()); b=Double.parseDouble(br.readLine()); c=Double.parseDouble(br.readLine()); disc=(b*b)-(4*a*c); if(disc==0) {
System.out.println("roots are real and equal "); x1=x2=-b/(2*a);
System.out.println("roots are "+x1+","+x2); }
else if(disc>0) {
x1=(-b+Math.sqrt(disc))/(2*a); x2=(-b+Math.sqrt(disc))/(2*a); System.out.println("roots are "+x1+","+x2); } else {
System.out.println("roots are imaginary"); }
} }
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Page 13Program Statement :
The Fibonacci sequence is defined by the following rule. The first 2 values in the sequence are 1, 1. Every subsequent value is the sum of the 2 values preceding it. Write a Java program that uses both recursive and non-recursive functions to print the nth value of the Fibonacci sequence.
Program :
/*Non Recursive Solution*/ import java.util.Scanner; class Fib {
public static void main(String args[ ]) {
Scanner input=new Scanner(System.in); int i,a=1,b=1,c=0,t; System.out.println("Enter value of t:"); t=input.nextInt(); System.out.print(a); System.out.print(" "+b); for(i=0;i<t-2;i++) { c=a+b; a=b; b=c; System.out.print(" "+c); } System.out.println();
System.out.print(t+"th value of the series is: "+c); }
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Page 15 /* Recursive Solution*/ import java.io.*; import java.lang.*; class Demo { int fib(int n) { if(n==1) return (1); else if(n==2) return (1); else return (fib(n-1)+fib(n-2)); } } class RecFibDemo {public static void main(String args[])throws IOException {
InputStreamReader obj=new InputStreamReader(System.in); BufferedReader br=new BufferedReader(obj);
System.out.println("enter last number"); int n=Integer.parseInt(br.readLine()); Demo ob=new Demo();
System.out.println("fibonacci series is as follows"); int res=0; for(int i=1;i<=n;i++) { res=ob.fib(i); System.out.println(" "+res); } System.out.println();
System.out.println(n+"th value of the series is "+res); }
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Page 17Program Statement :
WAJP that prompts the user for an integer and then prints out all the prime numbers up to that Integer.
Program : Import java.util.* class Test {
void check(int num) {
System.out.println ("Prime numbers up to "+num+" are:"); for (int i=1;i<=num;i++)
for (int j=2;j<i;j++) { if(i%j==0) break; else if((i%j!=0)&&(j==i-1)) System.out.print(“ “+i); } }
} //end of class Test class Prime {
public static void main(String args[ ]) { Test obj1=new Test();
Scanner input=new Scanner(System.in); System.out.println("Enter the value of n:"); int n=input.nextInt();
obj1.check(n); }
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Page 19Program Statement :
WAJP that checks whether a given string is a palindrome or not. Ex: MADAM is a palindrome.
Program : import java.io.*; class Palind {
public static void main(String args[ ])throws IOException { BufferedReader br=new BufferedReader(new
InputStreamReader(System.in));
System.out.println("Enter the string to check for palindrome:"); String s1=br.readLine();
StringBuffer sb=new StringBuffer(); sb.append(s1); sb.reverse(); String s2=sb.toString(); if(s1.equals(s2)) System.out.println("palindrome"); else System.out.println("not palindrome"); } }
Input &
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Page 21Program Statement :
WAJP for sorting a given list of names in ascending order. Program : import java.io.*; class Test { int len,i,j; String arr[ ]; Test(int n) { len=n; arr=new String[n]; }
String[ ] getArray()throws IOException {
BufferedReader br=new BufferedReader (new InputStreamReader(System.in));
System.out.println ("Enter the strings U want to sort----"); for (int i=0;i<len;i++)
arr[i]=br.readLine(); return arr;
}
String[ ] check()throws ArrayIndexOutOfBoundsException { for (i=0;i<len-1;i++) { for(int j=i+1;j<len;j++) { if ((arr[i].compareTo(arr[j]))>0) { String s1=arr[i]; arr[i]=arr[j]; arr[j]=s1; } } } return arr; }
System.out.println ("Sorted list is---"); for (i=0;i<len;i++)
System.out.println(arr[i]); }
} //end of the Test class class Ascend {
public static void main(String args[ ])throws IOException { Test obj1=new Test(4);
obj1.getArray(); obj1.check(); obj1.display(); }
}
Input & Output :
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Page 23Program Statement :
WAJP to multiply two given matrices. Program :
import java.util.*; class Test {
int r1,c1,r2,c2;
Test(int r1,int c1,int r2,int c2) { this.r1=r1;
this.c1=c1; this.r2=r2; this.c2=c2; }
int[ ][ ] getArray(int r,int c) { int arr[][]=new int[r][c];
System.out.println("Enter the elements for "+r+"X"+c+" Matrix:"); Scanner input=new Scanner(System.in);
for(int i=0;i<r;i++) for(int j=0;j<c;j++)
arr[i][j]=input.nextInt(); return arr;
}
int[ ][ ] findMul(int a[ ][ ],int b[ ][ ]) { int c[][]=new int[r1][c2];
for (int i=0;i<r1;i++) for (int j=0;j<c2;j++) { c[i][j]=0; for (int k=0;k<r2;k++) c[i][j]=c[i][j]+a[i][k]*b[k][j]; } return c; }
System.out.println ("The resultant "+r1+"X"+c2+" Matrix is:"); for (int i=0;i<r1;i++) {
for (int j=0;j<c2;j++)
System.out.print(res[i][j]+" "); System.out.println();
} }
} //end of Test class class MatrixMul {
public static void main(String args[ ])throws IOException { Test obj1=new Test(2,3,3,2);
Test obj2=new Test(2,3,3,2); int x[ ][ ],y[ ][ ],z[ ][ ];
System.out.println("MATRIX-1:");
x=obj1.getArray(2,3); //to get the matrix from user System.out.println("MATRIX-2:");
y=obj2.getArray(3,2);
z=obj1.findMul(x,y); //to perform the multiplication obj1.putArray(z); // to display the resultant matrix
} }
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Page 25Program Statement :
WAJP that reads a line of integers and then displays each integer and the sum of all integers. (use StringTokenizer class)
Program :
// Using StringTokenizer class import java.lang.*;
import java.util.*; class tokendemo {
public static void main(String args[ ]) { String s="10,20,30,40,50";
int sum=0;
StringTokenizer a=new StringTokenizer(s,",",false); System.out.println("integers are "); while(a.hasMoreTokens()) { int b=Integer.parseInt(a.nextToken()); sum=sum+b; System.out.println(" "+b); }
System.out.println("sum of integers is "+sum); }
}
// Alternate solution using command line arguments class Arguments {
public static void main(String args[ ]) {
int sum=0;
int n=args.length;
System.out.println("length is "+n);
int arr[]=new int[n]; for(int i=0;i<n;i++)
arr[i]=Integer.parseInt(args[i]);
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Page 27for(int i=0;i<n;i++)
System.out.println(arr[i]);
System.out.println("sum of enterd integers is:"); for(int i=0;i<n;i++)
sum=sum+arr[i]; System.out.println(sum);
} }
Input & Output :
Program Statement :
WAJP that reads on file name from the user, then displays information about whether the file exists, whether the file is readable, wheteher the file is writable, the type of file and the length of the file in bytes.
Program : import java.io.File; class FileDemo {
static void p(String s) { System.out.println(s); }
public static void main(String args[ ]) { File f1 = new File(args[0]);
p("File Name: " + f1.getName()); p("Path: " + f1.getPath());
p("Abs Path: " + f1.getAbsolutePath()); p("Parent: " + f1.getParent());
p(f1.exists() ? "exists" : "does not exist");
p(f1.canWrite() ? "is writeable" : "is not writeable"); p(f1.canRead() ? "is readable" : "is not readable"); p("is " + (f1.isDirectory() ? "" : "not" + " a directory")); p(f1.isFile() ? "is normal file" : "might be a named pipe"); p(f1.isAbsolute() ? "is absolute" : "is not absolute"); p("File last modified: " + f1.lastModified());
p("File size: " + f1.length() + " Bytes"); }
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Page 29Input & Output :
Program Statement :
WAJP that reads a file and displays the file on the screen, with a line number before each line.
Program : import java.io.*; class LineNum{
public static void main(String args[]){ String thisline;
for(int i=0;i<args.length;i++) {
try{
LineNumberReader br=new LineNumberReader(new FileReader(args[i])); while((thisline=br.readLine())!=null) { System.out.println(br.getLineNumber()+"."+thisline); } }catch(IOException e){ System.out.println("error:"+e); } } } }
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Page 31Program Statement :
WAJP that displays the number of characters, lines and words in a text file. Program :
import java.io.*; public class FileStat {
public static void main(String args[ ])throws IOException { long nl=0,nw=0,nc=0;
String line;
BufferedReader br=new BufferedReader(new FileReader(args[0])); while ((line=br.readLine())!=null) { nl++; nc=nc+line.length(); int i=0; boolean pspace=true; while (i<line.length()) { char c=line.charAt(i++); boolean cspace=Character.isWhitespace(c); if (pspace&&!cspace) nw++; pspace=cspace; } } System.out.println("Number of Characters"+nc); System.out.println("Number of Characters"+nw); System.out.println("Number of Characters"+nl); }}
// Alternate solution using StringTokenizer import java.io.*;
import java.util.*; public class FileStat {
public static void main(String args[ ])throws IOException { long nl=0,nw=0,nc=0;
String line;
BufferedReader br=new BufferedReader(new FileReader(args[0])); while ((line=br.readLine())!=null) {
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Page 33nc=nc+line.length();
StringTokenizer st = new StringTokenizer(line); nw += st.countTokens(); } System.out.println("Number of Characters"+nc); System.out.println("Number of Characters"+nw); System.out.println("Number of Characters"+nl); }}
Program Statement : WAJP that:
(a) Implements a Stack ADT
(b) Converts Infix expression to Postfix expression (c) Evaluates a Postfix expression
Program :
import java.io.*; interface stack {
void push(int item); int pop();
}
class Stackimpl {
private int stck[]; private int top; Stackimpl(int size) {
stck=new int[size]; top=-1;
}
void push(int item) {
if(top==stck.length-1)
System.out.println("stack is full insertion is not possible"); else
stck[++top]=item; }
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Page 35{
if(top==-1) {
System.out.println("stack is empty deletion is not possible"); return 0; } else return stck[top--]; } } class Stackdemo {
public static void main(String args[])throws IOException {
int a[];
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
System.out.println("enter the size of the array"); int n=Integer.parseInt(br.readLine());
Stackimpl obj1=new Stackimpl(n); a=new int[n];
System.out.println("enter numbers into the stack"); for(int i=0;i<n;i++)
a[i]=Integer.parseInt(br.readLine());
System.out.println("numbers are inserted"); for(int i=0;i<n;i++)
obj1.push(a[i]);
for(int i=0;i<n;i++)
System.out.println(" "+obj1.pop()); }
}
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Page 37Program Statement :
Write an Applet that displays a simple message. Program :
import java.awt.*; import java.applet.*; /*
<applet code = “HelloJava” width = 200 height = 60 > </applet>
*/
public class HelloJava extends Applet { public void paint(Graphics g) {
g.drawString(“Hello Java”, 10, 100); }
}
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Page 39Program Statement :
Write an Applet that computes the payment of a loan based on the amount of the loan, the interest rate and the number of months. It takes one parameter from the browser: Monthly rate; if true, the interest rate is per month, otherwise the interest rate is annual.
Program : import java.awt.*; import java.awt.event.*; import java.applet.*;
/* <applet code = "LoanPayment" width=500 height=300 > <param name = monthlyRate value=true>
</applet> */
public class LoanPayment extends Applet implements ActionListener { TextField amt_t, rate_t, period_t;
Button compute = new Button("Compute"); boolean monthlyRate;
public void init() {
Label amt_l = new Label("Amount: ");
Label rate_l = new Label("Rate: ", Label.CENTER); Label period_l = new Label("Period: ", Label.RIGHT);
amt_t = new TextField(10); rate_t = new TextField(10); period_t = new TextField(10); add(amt_l); add(amt_t); add(rate_l); add(rate_t); add(period_l); add(period_t);
add(compute); amt_t.setText("0"); rate_t.setText("0"); period_t.setText("0"); monthlyRate = Boolean.valueOf(getParameter("monthlyRate")); amt_t.addActionListener(this); rate_t.addActionListener(this); period_t.addActionListener(this); compute.addActionListener(this); }
public void paint(Graphics g) {
double amt=0, rate=0, period=0, payment=0; String amt_s, rate_s, period_s, payment_s;
g.drawString("Input the Loan Amt, Rate and Period in each box and press Compute", 50,100); try { amt_s = amt_t.getText(); amt = Double.parseDouble(amt_s); rate_s = rate_t.getText(); rate = Double.parseDouble(rate_s); period_s = period_t.getText(); period = Double.parseDouble(period_s); } catch (Exception e) { } if (monthlyRate)
payment = amt * period * rate * 12 / 100; else
payment = amt * period * rate / 100; payment_s = String.valueOf(payment);
g.drawString("The LOAN PAYMENT amount is: ", 50, 150); g.drawString(payment_s, 250, 150);
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Page 41}
public void actionPerformed(ActionEvent ae) { repaint();
} }
Input & Output :
Program Statement :
WAJP that works as a simple calculator. Use a grid layout to arrange buttons for the digits and for the + - x / % operations. Add atext field to display the result. Program :
import javax.swing.*; import java.awt.*; import java.awt.event.*;
//<applet code=Calculator height=300 width=200></applet> public class Calculator extends JApplet {
public void init() {
CalculatorPanel calc=new CalculatorPanel(); getContentPane().add(calc);
} }
class CalculatorPanel extends JPanel implements ActionListener { JButton
n1,n2,n3,n4,n5,n6,n7,n8,n9,n0,plus,minus,mul,div,dot,equal; static JTextField result=new JTextField("0",45);
static String lastCommand=null; JOptionPane p=new JOptionPane(); double preRes=0,secVal=0,res; private static void assign(String no) { if((result.getText()).equals("0")) result.setText(no); else if(lastCommand=="=") { result.setText(no); lastCommand=null; } else result.setText(result.getText()+no); } public CalculatorPanel() {
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Page 43setLayout(new BorderLayout()); result.setEditable(false);
result.setSize(300,200);
add(result,BorderLayout.NORTH); JPanel panel=new JPanel();
panel.setLayout(new GridLayout(4,4)); n7=new JButton("7"); panel.add(n7); n7.addActionListener(this); n8=new JButton("8"); panel.add(n8); n8.addActionListener(this); n9=new JButton("9"); panel.add(n9); n9.addActionListener(this); div=new JButton("/"); panel.add(div); div.addActionListener(this); n4=new JButton("4"); panel.add(n4); n4.addActionListener(this); n5=new JButton("5"); panel.add(n5); n5.addActionListener(this); n6=new JButton("6"); panel.add(n6); n6.addActionListener(this); mul=new JButton("*"); panel.add(mul); mul.addActionListener(this); n1=new JButton("1"); panel.add(n1); n1.addActionListener(this); n2=new JButton("2"); panel.add(n2); n2.addActionListener(this);
n3=new JButton("3"); panel.add(n3); n3.addActionListener(this); minus=new JButton("-"); panel.add(minus); minus.addActionListener(this); dot=new JButton("."); panel.add(dot); dot.addActionListener(this); n0=new JButton("0"); panel.add(n0); n0.addActionListener(this); equal=new JButton("="); panel.add(equal); equal.addActionListener(this); plus=new JButton("+"); panel.add(plus); plus.addActionListener(this); add(panel,BorderLayout.CENTER); }
public void actionPerformed(ActionEvent ae) {
if(ae.getSource()==n1) assign("1"); else if(ae.getSource()==n2) assign("2"); else if(ae.getSource()==n3) assign("3"); else if(ae.getSource()==n4) assign("4"); else if(ae.getSource()==n5) assign("5"); else if(ae.getSource()==n6) assign("6"); else if(ae.getSource()==n7) assign("7"); else if(ae.getSource()==n8) assign("8"); else if(ae.getSource()==n9) assign("9"); else if(ae.getSource()==n0) assign("0"); else if(ae.getSource()==dot) { if(((result.getText()).indexOf("."))==-1) result.setText(result.getText()+"."); } else if(ae.getSource()==minus)
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Page 45 { preRes=Double.parseDouble(result.getText()); lastCommand="-"; result.setText("0"); } else if(ae.getSource()==div) { preRes=Double.parseDouble(result.getText()); lastCommand="/"; result.setText("0"); } else if(ae.getSource()==equal) { secVal=Double.parseDouble(result.getText()); if(lastCommand.equals("/")) res=preRes/secVal; else if(lastCommand.equals("*")) res=preRes*secVal; else if(lastCommand.equals("-")) res=preRes-secVal; else if(lastCommand.equals("+")) res=preRes+secVal; result.setText(" "+res); lastCommand="="; } else if(ae.getSource()==mul) { preRes=Double.parseDouble(result.getText()); lastCommand="*"; result.setText("0"); } else if(ae.getSource()==plus) { preRes=Double.parseDouble(result.getText()); lastCommand="+"; result.setText("0"); } } }© Copyright
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Page 47Program Statement : WAJP for handling mouse events.
Program : import java.awt.*; import java.awt.event.*; import java.applet.*; /*
<applet code="MouseEvents" width=300 height=100> </applet>
*/
public class MouseEvents extends Applet
implements MouseListener, MouseMotionListener { String msg = "";
int mouseX = 0, mouseY = 0; // coordinates of mouse public void init() {
addMouseListener(this);
addMouseMotionListener(this); }
// Handle mouse clicked.
public void mouseClicked(MouseEvent me) { // save coordinates mouseX = 0; mouseY = 10; msg = "Mouse clicked."; repaint(); }
// Handle mouse entered.
public void mouseEntered(MouseEvent me) { // save coordinates
mouseX = 0; mouseY = 10;
msg = "Mouse entered."; repaint();
}
// Handle mouse exited.
public void mouseExited(MouseEvent me) { // save coordinates mouseX = 0; mouseY = 10; msg = "Mouse exited."; repaint(); }
// Handle button pressed.
public void mousePressed(MouseEvent me) { // save coordinates mouseX = me.getX(); mouseY = me.getY(); msg = "Down"; repaint(); }
// Handle button released.
public void mouseReleased(MouseEvent me) { // save coordinates mouseX = me.getX(); mouseY = me.getY(); msg = "Up"; repaint(); }
// Handle mouse dragged.
public void mouseDragged(MouseEvent me) { // save coordinates
mouseX = me.getX(); mouseY = me.getY(); msg = "*";
showStatus("Dragging mouse at " + mouseX + ", " + mouseY); repaint();
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Page 49}
// Handle mouse moved.
public void mouseMoved(MouseEvent me) { // show status
showStatus("Moving mouse at " + me.getX() + ", " + me.getY()); }
// Display msg in applet window at current X,Y location. public void paint(Graphics g) {
g.drawString(msg, mouseX, mouseY); }
}
Program Statement :
WAJP for creating multiple threads. Program :
class NewThread implements Runnable { String name; // name of thread
Thread t;
NewThread(String threadname) { name = threadname;
t = new Thread(this, name);
System.out.println("New thread: " + t); t.start(); // Start the thread
}
// This is the entry point for thread. public void run() {
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Page 51 for(int i = 5; i > 0; i--) { System.out.println(name + ": " + i); Thread.sleep(1000); } } catch (InterruptedException e) { System.out.println(name + "Interrupted"); } System.out.println(name + " exiting."); } } class MultiThreadDemo {public static void main(String args[]) { new NewThread("One"); // start threads new NewThread("Two");
new NewThread("Three"); try {
// wait for other threads to end Thread.sleep(10000);
} catch (InterruptedException e) {
System.out.println("Main thread Interrupted"); }
System.out.println("Main thread exiting."); }
Input & Output :
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Page 53Program Statement :
WAJP that correctly implements Producer-Consumer problem using the concept of Inter Thread Communication.
Program : class Q {
int n;
boolean valueSet = false; synchronized int get() {
if (!valueSet) try { wait(); } catch (InterruptedException e) { } System.out.println(“Got: “ + n); valueSet = false; notify(); return n; }
synchronized void put(int n) { if (valueSet) try { wait(); } catch (InterruptedException e) { } this.n = n; valueSet = true; System.out.println(“Put: “ + n); notify(); } }
class Producer implements Runnable { Q q;
Producer(Q q) { this.q = q;
new Thread(this, “Producer”).start(); }
public void run() { int i = 0; while(true) { q.put(i++); } } }
class Consumer implements Runnable { Q q;
Consumer(Q q) { this.q = q;
new Thread(this, “Consumer”).start(); }
public void run() { while(true) { q.get(); } } } class PC {
public static void main (String args[ ]) { Q q = new Q(); new Producer(q); new Consumer(q); System.out.println(“Press Ctrl-C to stop”); } }
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Page 55Program Statement :
WAJP that lets users create Pie charts. Design your own user interface (with Swings & AWT).
Program : import java.awt.*; import java.applet.*;
/*<applet code=PiChart.class width=600 height=600></applet>*/ public class PiChart extends Applet {
public void paint(Graphics g) { setBackground(Color.green); g.drawString("PI CHART",200,40); g.setColor(Color.blue); g.fillOval(50,50,150,150); g.setColor(Color.white); g.drawString("40%",130,160); g.setColor(Color.magenta); g.fillArc(50,50,150,150,0,90); g.setColor(Color.white); g.drawString("25%",140,100); g.setColor(Color.yellow); g.fillArc(50,50,150,150,90,120); g.setColor(Color.black); g.drawString("35%",90,100); g.setColor(Color.yellow); g.fillOval(250,50,150,150); g.setColor(Color.black); g.drawString("15%",350,150); g.setColor(Color.magenta); g.fillArc(250,50,150,150,0,30); g.setColor(Color.black); g.drawString("5%",360,120); g.setColor(Color.blue);
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Page 57 g.fillArc(250,50,150,150,30,120); g.setColor(Color.white); g.drawString("30%",330,100); g.setColor(Color.black); g.fillArc(250,50,150,150,120,180); g.setColor(Color.white); g.drawString("50%",280,160); } }© Copyright
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Page 59Program Statement :
WAJP that allows user to draw lines, rectangles and ovals. Program :
import javax.swing.*; import java.awt.Graphics;
public class choice extends JApplet {
int i,ch;
public void init() {
String input;
input=JOptionPane.showInputDialog("enter your choice(1-lines,2-rectangles,3-ovals)");
ch=Integer.parseInt(input); }
public void paint(Graphics g) { switch(ch) { case 1:{ for(i=1;i<=10;i++) { g.drawLine(10,10,250,10*i); } break; } case 2:{ for(i=1;i<=10;i++) { g.drawRect(10*i,10*i,50+10*i,50+10*i); } break; } case 3:{ for(i=1;i<=10;i++)
{
g.drawOval(10*i,10*i,50+10*i,50+10*i); }
break; }}}}
Program Statement :
WAJP that implements a simple client/server application. The client sends data to a server. The server receives the data, uses it to produce a result and then sends the result back to the client. The client displays the result on the console. For ex: The data sent from the client is the radius of a circle and the result produced by the server is the area of the circle.
Program : // Server Program import java.io.*; import java.net.*; import java.util.*; public class Server {
public void static main (String args [ ] ) { try {
// create a server socket
ServerSocket s = new ServerSocket(8000); // start listening for connections on srver socket Socket connectToClient = s.accept();
// create a buffered reader stream to get data from client BufferedReader isFromClient = new BufferedReader(new InputStreamReader (connectToClient.getInputStream()));
// create a buffer reader to send result to client PrintWriter osToClient = new
PrintWriter(connectToClient.getOutputStream(), true);
// continuously read from client, process, send back while (true) {
// read a line and create string tokenizer StringTokenizer st = new
StringTokenizer(isFromClient.readLine());
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Page 63double radius = new Double(st.nextToken()).doubleValue();
// display radius on console
System.out.println(“Radius received from client: “ + radius);
// comput area
double area = radius * radius *Math.PI; // send result to client
osToClient.println(area); // print result on console
System.out.println(“Area found: “ +area); } } catch (IOException e) { System.err.println(e); } } } // Client Program import java.io.*; import java.net.*; import java.util.*; public class Client {
public void static main (String args [ ] ) { try {
// create a socket to connect to server
Socket connectToServer = new Socket(“local host”, 8000); // create a buffered input stream to get result from server BufferedReader isFromServer = new BufferedReader(new InputStreamReader (connectToServer.getInputStream()));
// create a buffer output stream to send data to server PrintWriter osToServer = new
PrintWriter(connectToClient.getOutputStream(), true); // continuously send radius and get area while (true) {
Scanner input=new Scanner(System.in); System.out.print(“Please enter a radius: “); double radius =input.nextDouble();
// display radius on console osToServer.println(radius); // get area from server StringTokenizer st = new StringTokenizer(isFromServer.readLine());
// convert string to double Double area = new
Double(st.nextToken()).doubleValue();
// print result on console
System.out.println(“Area received from the server is: “ +area); } } catch (IOException e) { System.err.println(e); } } }
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Page 65Input & Output :
Program Statement :
WAJP that illustrates how runtime polymorphism is achieved. Program : class Figure { double dim1; double dim2; Figure(double a, double b) { dim1 = a; dim2 = b; } double area() {
System.out.println("Area for Figure is undefined."); return 0;
} }
class Rectangle extends Figure { Rectangle(double a, double b) { super(a, b);
}
// override area for rectangle double area() {
System.out.println("Inside Area for Rectangle."); return dim1 * dim2;
} }
class Triangle extends Figure { Triangle(double a, double b) { super(a, b);
}
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Page 67double area() {
System.out.println("Inside Area for Triangle."); return dim1 * dim2 / 2;
} }
class FindAreas {
public static void main(String args[]) { Figure f = new Figure(10, 10);
Rectangle r = new Rectangle(9, 5); Triangle t = new Triangle(10, 8); Figure figref; figref = r; System.out.println("Area is " + figref.area()); figref = t; System.out.println("Area is " + figref.area()); figref = f; System.out.println("Area is " + figref.area()); } }
Input & Output :
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Page 69Program Statement :
WAJP to generate a set of random numbers. Find its sum and average. The program should also display ‘*’ based on the random numbers generated. Program :
import java.util.*; class RandNum {
public static void main(String ax[ ]) { int a[ ]=new int[5];
int sum=0;
Random r=new Random(); for (int i=0;i<5;i++) {
a[i]=r.nextInt(10); System.out.print(a[i]); for(int y=0;y<a[i];y++) System.out.print(" *"); System.out.println(""); } for(int i=0;i<5;i++) sum=sum+a[i]; System.out.println("Sum="+sum); System.out.println("Avg="+(double)sum/a.length); } }
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Page 71Program Statement :
WAJP to create an abstract class named Shape, that contains an empty method named numberOfSides(). Provide three classes named Trapezoid, Triangle and Hexagon, such that each one of the classes contains only the method
numberOfSides(), that contains the number of sides in the given geometrical figure.
Program : abstract class Shape {
abstract void numberOfSides(); }
class Trapezoid extends Shape{ void numberOfSides() {
System.out.println(" Trapezoidal has four sides"); }
}
class Triangle extends Shape { void numberOfSides() {
System.out.println("Triangle has three sides"); }
}
class Hexagon extends Shape { void numberOfSides() {
System.out.println("Hexagon has six sides"); }
}
class ShapeDemo {
public static void main(String args[ ]) { Trapezoid t=new Trapezoid(); Triangle r=new Triangle(); Hexagon h=new Hexagon(); Shape s;
s=t;
s=r; s.numberOfSides(); s=h; s.numberOfSides(); } }
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Page 73Program Statement :
WAJP to implement a Queue, using user defined Exception Handling (also make use of throw, throws).
Program :
import java.util.Scanner;
class ExcQueue extends Exception { ExcQueue(String s) { super(s); } } class Queue { int front,rear;
int q[ ]=new int[10]; Queue() {
rear=-1; front=-1; }
void enqueue(int n) throws ExcQueue { if (rear==9)
throw new ExcQueue("Queue is full"); rear++;
q[rear]=n; if (front==-1) front=0; }
int dequeue() throws ExcQueue { if (front==-1)
throw new ExcQueue("Queue is empty"); int temp=q[front];
if (front==rear) front=rear=-1;
else front++; return(temp); } } class UseQueue {
public static void main(String args[ ]) { Queue a=new Queue();
try { a.enqueue(5); a.enqueue(20); } catch (ExcQueue e) { System.out.println(e.getMessage()); } try { System.out.println(a.dequeue()); System.out.println(a.dequeue()); System.out.println(a.dequeue()); } catch(ExcQueue e) { System.out.println(e.getMessage()); } } }
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Page 75Program Statement :
WAJP that creates 3 threads by extending Thread class. First thread displays “Good Morning” every 1 sec, the second thread displays “Hello” every 2 seconds and the third displays “Welcome” every 3 seconds. (Repeat the same by
implementing Runnable) Program :
// Using Thread class
class One extends Thread { public void run() {
for ( ; ; ) { try{ sleep(1000); }catch(InterruptedException e){} System.out.println("Good Morning"); } } }
class Two extends Thread { public void run() {
for ( ; ; ) { try{ sleep(2000); }catch(InterruptedException e){} System.out.println("Hello"); } } }
class Three extends Thread { public void run() {
for ( ; ; ) { try{
sleep(3000);
}catch(InterruptedException e){} System.out.println("Welcome");
} }
}
class MyThread {
public static void main(String args[ ]) { Thread t = new Thread();
One obj1=new One(); Two obj2=new Two(); Three obj3=new Three(); Thread t1=new Thread(obj1); Thread t2=new Thread(obj2); Thread t3=new Thread(obj3); t1.start(); try{ t.sleep(1000); }catch(InterruptedException e){} t2.start(); try{ t.sleep(2000); }catch(InterruptedException e){} t3.start(); try{ t.sleep(3000); }catch(InterruptedException e){} } }
// Using Runnable interface
class One implements Runnable { One( ) {
new Thread(this, "One").start(); try{
Thread.sleep(1000);
}catch(InterruptedException e){} }
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Page 77public void run() { for ( ; ; ) { try{ Thread.sleep(1000); }catch(InterruptedException e){} System.out.println("Good Morning"); } } }
class Two implements Runnable { Two( ) {
new Thread(this, "Two").start(); try{
Thread.sleep(2000);
}catch(InterruptedException e){} }
public void run() { for ( ; ; ) { try{ Thread.sleep(2000); }catch(InterruptedException e){} System.out.println("Hello"); } } }
class Three implements Runnable { Three( ) {
new Thread(this, "Three").start(); try{
Thread.sleep(3000);
}catch(InterruptedException e){} }
public void run() { for ( ; ; ) { try{ Thread.sleep(3000); }catch(InterruptedException e){} System.out.println("Welcome"); } } } class MyThread {
public static void main(String args[ ]) { One obj1=new One();
Two obj2=new Two(); Three obj3=new Three(); }
}
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Page 79Program Statement :
WAJP that will compute the following series: (a) 1 + 1/2 + 1/3+ …….+ 1/n (b) 1 + 1/2 + 1/ 22 + 1/ 23 + … … + 1/ 2n (c) ex = 1 + x/1! + x2/2! + x3/3! + … … Program : // (a) 1 + 1/2 + 1/3+ …….+ 1/n import java.util.Scanner; class Series1 {
public static void main(String arg[ ]) { int n;
double sum=0,i;
Scanner input= new Scanner(System.in); System.out.println("enter value of n:"); n=input.nextInt(); for(i=1;i<=n;i++) sum=sum+(double)(1/i); System.out.println("Result:"+sum); } }
// (b) 1 + 1/2 + 1/ 2 + 1/ 2 + … … + 1/ 2 import java.util.Scanner;
class Series2 {
public static void main(String arg[ ]) { int n;
double sum=0,i;
Scanner input= new Scanner(System.in); System.out.println("enter value of n:"); n=input.nextInt(); for(i=1;i<=n;i++) sum=sum+(double)(1/Math.pow(2,i-1)); System.out.println("Result:"+sum); } }
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Page 81// (c) ex = 1 + x/1! + x2/2! + x3/3! + … … import java.util.*;
class Series3{
public static void main(String arg[ ]) { int n,x;
double sum=0,i,d=1;
Scanner input= new Scanner(System.in); System.out.println("enter value of n:"); n=input.nextInt(); System.out.println("enter value of x:"); x=input.nextInt(); for (i=1;i<=n;i++) { sum=sum+(double)((Math.pow(x,i-1)/d)); d=d*i; } System.out.println("Result :"+sum); } }
Program Statement : WAJP to do the following:
(a) To output the question “Who is the inventor of Java?” (b) To accept an answer
(c) To printout “GOOD” and then stop if the answer is correct (d) To output the message “TRY AGAIN”, if the answer is wrong
(e) To display the correct answer, when the answer is wrong even at the third attempt
Program : import java.io.*; class Ask {
public static void main(String a[ ])throws Exception { String str1,str2;
int count=0;
str1="James Gosling";
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
System.out.println("Who is the inventor of Java ?"); while(count!=3) { str2=br.readLine(); if(str1.equalsIgnoreCase(str2)) { System.out.println("!!! GOOD !!!"); break; } else { if(count<2) System.out.println("TRY AGAIN !"); count++; } } if(count==3) System.out.println("Correct Answer is : "+str1); } }
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Page 83Input & Output :
Program Statement :
WAJP to transpose a matrix using ‘arraycopy’ command. Program :
class TransMatrix {
public static void main(string args[ ]) { int i,j,k=0; int rows,cols,r,c; int a[ ][ ]={{1,2,3,4},{5,6,7,8}}; rows=a.length; cols=a[0].length;
int b[ ][ ]=new int[rows*cols]; int s[ ]=new int[rows*cols]; int d[ ]=new int[rows*cols]; for (i=0;i<rows;i++) for (j=0;j<cols;j++,k++) s[k]=a[i][j]; i=j=k=r=c=0; while(r<rows) { while(c<cols) { System.arraycopy(s,i,d,i,l); b[j++][k]=d[i++]; c++; } j=c=0; k++; t++; } System.out.println("a matrix:"); for (i=0;i<rows;i++) { for(j=0;j<cols;j++) System.out.print(" "+a[i][j]); System.out.println(); }
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Page 85 System.out.println("\nb matrix:"); for(i=0;i<cols;i++) { for(j=0;j<rows;j++) System.out.print(" "+b[i][j]); System.out.println(); } } }Input & Output : INPUT :
Program Statement :
Create an inheritance hierarchy of Rodent, Mouse, Gerbil, Hamster etc. In the base class provide methods that are common to all Rodents and override these in the derived classes to perform different behaviors, depending on the specific type of Rodent. Create an array of Rodent, fill it with different specific types of Rodents and call your base class methods.
Program : import java.util.Random; class Rodent{ void place() {} void tail() {} void eat() {}
public static Rodent randRodent(){ Random rr=new Random(); switch (rr.nextInt(4)) {
case 0: return new Mouse(); case 1: return new Gerbil (); case 2: return new Hamster (); case 3: return new Beaver (); }
return new Rodent(); }
}
class Mouse extends Rodent { void place() {
System.out.println(“Mice are found all over the world”); }
void tail() {
System.out.println(“Mice have long and hairless tail”); }
void eat() {
System.out.println(“Mice eat cardboards, papers, clothes”);
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Page 87}
class Gerbil extends Rodent { void place() {
System.out.println(“Gerbils are found in arid parts of Africa and Asia”);
}
void tail() {
System.out.println(“Gerbils have long tail”); }
void eat() {
System.out.println(“Gerbils eat seeds, roots, insects, parts of plants”);
} }
class Hamster extends Rodent { void place() {
System.out.println(“Hamsters are found in Western Europe to China – Dry regions only”);
}
void tail() {
System.out.println(“Hamsters have short tail”); }
void eat() {
System.out.println(“Hamsters eat cereals”); }
}
class Beaver extends Rodent { void place() {
System.out.println(“Beavers are found in Northern Europe and North America”);
}
void tail() {
System.out.println(“Beavers have broad tail”); }
void eat() {
} }
public class Rodents{
public static void main(String args[ ]) { Rodent r[] = new Rodent[6]; for (int i=0; i<r.length; i++)
r[i] = Rodent.randRodent(); for (int i=0; i<r.length; i++) {
r[i].place(); r[i].tail(); r[i].eat(); } } }
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Page 89Input & Output :
Program Statement :
WAJP to print a chessboard pattern. Program :
import java.awt.*; import java.applet.*;
public class ChessBoard extends Applet {
/* This applet draws a red-and-black checkerboard. It is assumed that the size of the applet is 160 by 160 pixels.
*/
/* <applet code="ChessBoard.class" width=200 height=160> </applet> */
public void paint(Graphics g) {
int row; // Row number, from 0 to 7 int col; // Column number, from 0 to 7 int x,y; // Top-left corner of square
for ( row = 0; row < 8; row++ ) { for ( col = 0; col < 8; col++) { x = col * 40; y = row * 40; if ( (row % 2) == (col % 2) ) g.setColor(Color.white); else g.setColor(Color.black); g.fillRect(x, y, 40, 40); }
} // end for row } // end paint() } // end class
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Page 91
VIVA VOCE QUESTIONS
1) What is a method? And What is OOPS?
2) What is the signature of a method?
3) What is the difference between an instance variable and a class
variable?
4) What is an abstract method?
5) What is an abstract class?
6)What is an object reference?
7) What is an exception?
8) Why does the compiler complain about Interrupted Exception when I
try to use Thread's sleep method?
9) Why do methods have to declare the exceptions they can throw?
10) What's the difference between a runtime exception and a plain
exception-why don't you runtime exceptions have to be declared?
11) What is an applet?
12) . How do applets differ from applications?
13) . Can I write Java code that works both as an applet and as a
stand-alone application?
14). What is the difference between an application, an applet, and a
servlet?
15) Several applet methods seem special, in that I need to define them
even if my own code doesn't invoke them--what are the methods, and
when (and by whom) are they invoked?
16). Should applets have constructors?
17) . How can my applet tell when a user leaves or returns to the web
page containing my applet?
18) . How do I read number information from my applet's parameters,
given that Applet's getParameter method returns a String?
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Page 9319) . When I subclass Applet, why should I put setup code in the init()
method? Why not just a constructor for my class?
20). Can I use an http URL to write to a file on the server from an
applet?
21) . Can applets launch programs on the server?
22) . Can applets launch programs on the client?
23) . How do you do file I/O from an applet?
24) . How do I access remote machine's file system through Java
Applet?
25) What is a thread?
26) . How do I create a thread and start it running?
27) . How many threads can I create?
28) . How does Thread's stop method work--can I restart a stopped
thread?
29) . If I create a thread, and then null out the reference to it, what
happens to the thread? Does it get interrupted or what?
30) . How should I stop a thread so that I can start a new thread later in
its place?
31) .How do I specify pause times in my program?
32) Why is thread synchronization important for multithreaded
programs?
33) . What is a monitor?
34) . How does the synchronized keyword work?
35) . What objects do static synchronized methods use for locking?
36) . How do the wait and notifyAll/notify methods enable cooperation
between threads?
37) . How do I achieve the effect of condition variables if the Java
platform provides me with only wait and notifyAll/notify methods?
38) . How do I make one thread wait for one or more other threads to
finish?
39) . What do I use the yield method for?
40) . Does the Java Virtual Machine protect me against deadlocks?
41) . I have several worker threads. I want my main thread to wait for
any of them to complete, and take action as soon as any of them
completes. I don't know which will complete soonest, so I can't just call
Thread.join on that one. How do I do it?
42) How do I do keyboard (interactive) I/O in Java?
43) . Is there a way to read a char from the keyboard without having to
type carriage-return?
44). How do I read a line of input at a time?
45) . How do I read input from the user (or send output) analogous to
using standard input and standard output in C or C++?
46) . Is there a standard way to read in int, long, float, and double values
from a string representation?
47) . How do I read a String/int/boolean/etc from the keyboard?
48) . I try to use "int i = System.in.read();" to read in an int from the
standard input stream. It doesn't work. Why?
49) . I use the following to read an int. It does not work. Why?
50). I'm trying to read in a character from a text file using the
DataInputStream's readChar() method. However, when I print it out, I
get?’s.
51) . Why do I get garbage results when I use DataInputStream's readInt
or readFloat methods to read in a number from an input string?
52). How do I read data from a file?
53) . How do I write data to a file?
54). How do I append data to a file?
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