Input using Scanner Object
Java Scanner class comes under the java.util package. Java has various ways to read input from the keyboard, the java.util.Scanner class is one of them.
Syntax to Declare object of Scanner class
Scanner scan = new Scanner(System.in);
Syntax to take input
Scannerobject.nextDatatype()
Example Scanner Object
import java.util.Scanner;
public class ScannerClassExample1 { public static void main(String args[])
{
System.out.println("---Enter Your Details--- "); Scanner in = new Scanner(System.in);
System.out.print("Enter your name: ");
String name = in.next(); or in.nextLine(); // String input System.out.println("Name: " + name);
System.out.print("Enter your age: "); int i = in.nextInt();
System.out.println("Age: " + i);
System.out.print("Enter your salary: "); double d = in.nextDouble();
System.out.println("Salary: " + d); in.close();
Arrays
Java array is an object the contains elements of similar data type. It is a data
structure where we store similar elements. We can store only fixed set of elements in a java array.
Array in java is index based, first element of the array is stored at 0 index.
Types of Array in java - There are two types of array.
Arrays
Syntax to Declare an Array in java
dataType[] arr = new datatype[size];
(or)
dataType arr[]= new datatype[size];
Example1
-class Testarray{public static void main(String args[]){
int a[]=new int[5]; //declaration and instantiation a[0]=10;//initialization
a[1]=20; a[2]=70; a[3]=40; a[4]=50;
//printing array
for(int i=0;i<a.length;i++) //length is the property of array System.out.println(a[i]);
Arrays
Example-2
class Testarray1
{
public static void main(String args[])
{
int a[]={33,3,4,5};
//declaration, instantiation and initialization//printing array
for(int i=0;i<a.length;i++)
//length is the property of arrayArrays
Example-3 Sum of array elements
class array_sum
{
public static void main(String args[])
{
int a[]={33,3,4,5};
//declaration, instantiation and initialization int sum=0;//sum array
for(int i=0;i<a.length;i++)
//length is the property of arraysum=sum+a[i];
System.out.println(“Sum=“+sum);
}
Arrays
Example-4 search element in array
class array_sum
{
public static void main(String args[])
{
int a[]={33,3,4,5};
//declaration, instantiation and initialization int e;//sum array
for(int i=0;i<a.length;i++)
//length is the property of arraysum=sum+a[i];
Pass Array to function
We can pass the java array to method so that we can reuse the same logic
on any array.
Syntax to declare function as array parameter
Returntype functionname (datatype array[])
{
}
Syntax to call function as pass array
Pass Array to function
Example-1 – function to sum array elements
Import java.util.Scanner; class sum_arr
{
int sumarr(int a[]) // function declaration and definition
{
int sum=0, I;
for(i=0;i<a.length;i++) sum=sum+a[i]; return(sum);
}
public static void main(String ar[]) {
int a[]=new int[5];
Scanner sc=new Scanner(System.in); for(i=0;i<5;i++)
a[i]=sc.nextInt();
int sum=sumarr(a); // function call
Pass Array to function
Example-2 – function to search element in array
Import java.util.Scanner; class search_arr
{
void sear_arr(int a[], int e) // function declaration and definition
{
int sum=0, I;
for(i=0;i<a.length;i++) {
if(e==a[i]) {
System.out.println (“Found”);
System.exit(0); // normal exit from program }
}
Pass Array to function
Example-2 continue – function to search element in array
public static void main(String ar[]) {
int a[]=new int[5];
Scanner sc=new Scanner(System.in); for(i=0;i<5;i++)
a[i]=sc.nextInt(); int e;
System.out.println(“Enter no to search :”); e=sc.nextInt();
sear_arr(a,e); // function call
Pass Array to function
Example-3 – function to find max element in 10 numbers
Import java.util.Scanner; class search_arr
{
int max_arr(int a[],) // function declaration and definition
{
int max=a[0], I;
for(i=0;i<a.length;i++) {
if(a[i]>max) {
max=a[i]; }
}
Pass Array to function
Example-3 continue – function to search element in array
public static void main(String ar[]) {
int a[]=new int[10];
Scanner sc=new Scanner(System.in); for(i=0;i<5;i++)
a[i]=sc.nextInt();
int max=max_arr(a); // function call
System.out.println(“Max no =“+max); }
String and String Methods
•
String is a sequence of characters. But in Java, a string is an
object that represents a sequence of characters.
Example
-String a=“amit”;
or
String s;
s=“amit”;
Methods
1.
length() – give the number of elements in array.
Example –
String s=“kiran”;
String Methods
2. charAt(index) – find the character at the specified index.
Example –
String s=“dit”;
System.out.println(s.charAt(1)); // display “I” (s[0] –d, s[1]- I, s[2]-t)
3. substring(int) – display all characters from specified index.
String s=“dehradun”;
System.out.println(s.substring(2)); //display “radun”
4. concat(string)- join string2 in string1
String s1=“abc”; //string1
String s2=“xyz”; //string2
S1.contact(s2);
String Methods
2. charAt(index) – find the character at the specified index.
Example –
String s=“dit”;
System.out.println(s.charAt(1)); // display “I” (s[0] –d, s[1]- I, s[2]-t)
3. substring(int) – display all characters from specified index.
String s=“dehradun”;
System.out.println(s.substring(2)); //display “radun”
4. concat(string)- join string2 in string1
String s1=“abc”; //string1
String s2=“xyz”; //string2
S1.contact(s2);
String Methods
5. indexof(string) - give - find the index of specified string.
Example –
String s=“dit”;
System.out.println(s.indexOf(“it”));
// display 16. equals(string) – will return true if string1 is equal to string2.
String s1=“dehradun”;
String s2=“dehra”;
System.out.println(s1.substring(s2)); //display false
7. equalsIgnoreCase(string)- will match string1 with string2 by ignoring
case.
String s1=“dit”; //string1
String s2=“DIT”; //string2
String Methods
8. compareTo(string) – compare string1 with string2.
Return 0 – if string1 =string2 Return <0 - if string1<string2
Return >0 if string1 is greater than string2
Example –
String s1=“dit”; String s2=“abc”;
If(s1.compareTo(s2))>0
System.out.println(“s1 is smaller than s2”); else
System.out.println(“s2 is smaller than s1”);
9. toLowerCase() – return string in lower case.
String s1=“DIT”;
String s2=s1.toLowerCase()l System.out.println(s2);
10. toUpperCase()- return string in upper case.
String s1=“dit”;
String Methods: Example
Write a program to compare two strings
-import java.util.Scanner; class compare_str
{
public static void main(String ar[]) {
Scanner sc=new Scanner(System.in); System.out.println("ENter 1st String :"); String s1=sc.next();
System.out.println("ENter 2nd String :"); String s2=sc.next();
if(s1.compareTo(s2)==0)
System.out.println("Strings are equal"); if(s1.compareTo(s2)>0)
System.out.println("Strings1 is greater than String2"); if(s1.compareTo(s2)<0)
String array
•
A Java String Array is an object that holds a fixed number of
String values.
Syntax –
String[] object =new String[size];
Or
String object[] =new String[size];
Example –
String name[]=new String[5];
name[0]=“Amit”;
String array
String array
initialization-String[] a1 = {"AAA", "BBB", "CCC", "DDD", "EEE"};
This array a1 will store 5 value from a1[0] to a1[4]
Example –
String[] a1 = {"Apple", "Banana", "Orange"};
for( int i = 0; i < a1.length; i++)
{
Dynamic array
Static array
-•
If the array is defined in such a way where, at the time of
declaration size is mentioned. It is called as static array.
Example – int a[]=new int[size];
•
Main drawback of this declaration is memory wastage.
Example –
Int a[]=new int[10];
a[0]=1;
a[1]=2;
•
In above example 2 to 8 rest elements are not stored but
memory is allocated, so wasted.
Total memory
waste-Let int takes 4 bytes for one
Dynamic array
Dynamic array
-•
If the array is defined in such a way where, at the time of
declaration size is not mentioned. It is called as dynamic array.
•
In java for dynamic array we use a class called as – ArrayList()
•
This class uses a package – import java.util.ArrayList
•
Syntax-ArrayList<Wrraper class /Class name> var=new ArrayList<>();
Example –
ArrayList<String> a1=new ArrayList<>();
ArrayList<Integer> a2=new ArrayList<>();
Wrapper Classes in Java. A Wrapper class is a class whose object
wraps or contains a primitive data types.
Dynamic array
import java.util.ArrayList;
class arraylist
{
public static void main(String ar[])
{
ArrayList<String> a1=new ArrayList<>();
a1.add("Garima");
a1.add("Reema");
System.out.println(a1);
// print all values
}
}
To print all
Dynamic array
Methods of ArrayList –
1.
add(value) – use to add new value in arraylist
2.
get(indexno) – use to display element store at the index no.
3.
add(indexno, value) – add value at particular indexno and existing value will
shift to next index.
Example –
ArrayList<String> a1=new ArrayList<>();
a1.add("Garima"); //a1[0]
a1.add("Reema"); // a1[1]
System.out.println(a1.get(0)); // print “garima”
a1.add(1,"Sonu"); // a1[1]=sonu
System.out.println(a1); // Garima, Sonu, Reema
4. remove(indexno) - remove value stored at the indexno.
Dynamic array
Methods of ArrayList –5. clear() – remove all value from arraylist. Example
-import java.util.ArrayList; class arraylist
{
public static void main(String ar[]) {
ArrayList<String> a1=new ArrayList<>(); // store String values ArrayList<Integer> a2=new ArrayList<>(); // store integer values a1.add("Garima"); a1.add("Reema"); a1.add(1,"Sonu"); a2.add(1); a2.add(2); System.out.println(a1.get(0)); System.out.println(a1); a1.remove(0);
System.out.println("All values :"+a1); for(int i = 0; i < a1.size(); i++) {
