Convert String to Integer

 

public class str{
    public static void main(String args[])
    {
        String a="1";
        int x=Integer.parseInt(a);

    }
}

String Buffer

 

 

public class strbuf
{
    public static void main(String args[])
    {
        String str1="Hello";
        StringBuffer strbuf=new  StringBuffer(str1);
        str1= strbuf.append("World").toString();
        System.out.println(str1);
    }
}

Search Number of Occurrences in String

import java.util.Scanner;

public class demo{
    public static void main(String args[])
    {
        char input;
        String str_input;
        char veb;
        int count=0;
        String str="Apple";
        Scanner scan=new Scanner(System.in);
        System.out.println("Enter a String");
        str=scan.nextLine();
        System.out.println("enter the Charchter you want to Search");
        str_input=scan.next();
        input=str_input.charAt(0);
        for(int i=0;i<str.length();i++)
        {
            veb=str.charAt(i);
            if(input==veb)
            {
                count++;
            }       
        }
            System.out.println("Occurances : "+count);
    }
}

Get Sum of numbers passing a Array to a Method

 

import java.util.Scanner;

public class avg{
    public static void main(String args[])
    {
        Scanner scan = new Scanner(System.in);
        double avg;
        int input[]=new int[5];
        System.out.print("Enter Values : ");
        for(int i=0;i<input.length;i++)
        {
            input[i]=scan.nextInt();   
        }
        avg=getsum(input);
        System.out.println("Sum is : "+avg);
    }
    public static double  getsum(int[] arr)   
    {
        double sum=0;
        for(int j=0;j<arr.length;j++)
        {
            sum=arr[j]+sum;
        }   
        return sum;
    }

}

Find Odd numbers and even

 

import java.util.Scanner;

public class odd
{
    public static void main(String args[])
    {
        Scanner scan=new Scanner(System.in);
        int[] arr;
        arr=new int[5];
        int[] arr_odd=new int[5];
        int[] arr_eve=new int[5];
        int odd=0;
        System.out.print("Enter 5 Numbers : ");
        for(int i=0;i<arr.length;i++)
        {           
            arr[i]=scan.nextInt();
            odd=arr[i]%2;
            if(odd==0)
            {
                arr_odd[i]=arr[i];
            }
            else
            {
                arr_eve[i]=arr[i];
            }
        }
            for(int j=0;j<arr_odd.length;j++)
            {
                System.out.println(arr_odd[j]);
            }
    }
}

Random Boolean Number

 

 

import java.util.Random;

public class bole
{
    public static void main(String args[])
    {
        Random rand=new Random();
        boolean bool;
        bool=rand.nextBoolean();
        System.out.println(bool);
    }
}

Generate a Random Number

 

import java.util.Random;

public class rand
{
    public static void main(String args[])
    {
        int val=0;
        Random myran = new Random();
        for(int i=0;i<5;i++)
        {
            val= myran.nextInt(5);
            System.out.println(val);
        }
    }
}

Find Maximum Number

 

import java.util.Scanner;

public class maxnum
{
    public static void main(String args[])
    {
        Scanner myScanner = new Scanner(System.in);
        int uBound=3;
        int NUM_MAX=0;
        int NUM_MIN;
        System.out.println("How Many Numbers");
        uBound=myScanner.nextInt();
        int[] arr;
        arr=new int[uBound];
        System.out.println("Enter "+arr.length+" Numbers : ");
        for(int i=0;i<arr.length;i++)
        {
            arr[i]=myScanner.nextInt();
            if(arr[i]>NUM_MAX)
            {
                NUM_MAX=arr[i];
            }
        }
        System.out.println("Maximum Number is : "+NUM_MAX);
    }
}

Reverse a Array

 

import java.util.Scanner;

public class arrrev
{
    public static void main (String args[])       
    {
        Scanner scan=new Scanner(System.in);
        int max=0;
        int arr[];
        int rev_arr[];
        arr=new int[3];
        rev_arr=new int[3];
        System.out.println("Enter the Arrary");
        for(int i=0;i<arr.length;i++)
        {
            arr[i]=scan.nextInt();
        }
        for(int j=arr.length;j>0;j--)
        {
            rev_arr[j]=arr[j];
        }
        for(int x=0;x<arr.length;x++)
        {
            System.out.println(rev_arr[x]);
        }
    }
}

Read Input to an Array

 

import java.util.Scanner;

public class arrstr
{
    public static void main(String args[])
    {
        Scanner scan=new Scanner(System.in);
        int[] arr;
        arr=new int[5];
        int i=0;
        System.out.println("Enter Values : ");
        for(;i<5;i++)
        {
            arr[i]=scan.nextInt();
        }
          for(i=0;i<5;i++)
        {
            System.out.println(" "+arr[i]);
        }
    }

}

Declare an Array

 

public class arrstr
{
    public static void main(String args[])
    {
        char[] arr;
        arr= new char[5];
    }
}

Sub Strings

public class substr
{
    public static void main (String args[])
    {
        String str="ArchAngel";
        String output;
        output=str.substring(4);
        System.out.print("Sub String : "+output);
    }
}

Replace a Character in a String

 

public class strrep
{
    public static void main(String args[])
    {
        char oldchar='A';
        char newchar='Z';
        String str="AAA";

        System.out.println("Old String : "+str);

        str=str.replace(oldchar,newchar);

        System.out.println("New String :"+str);
    }
}

Concatenate Two Strings

 

public class strcon
{
    public static void main (String args[])
    {
        String str1="Hello";
        String str2="World";
        String output;
        output=str1.concat(str2);
        System.out.print(output);
    }
}

Get a Letter from a String

 

 

import java.util.Scanner;

public class charstr

{
    public static void main (String args[])
    {
        Scanner strscan=new Scanner(System.in);

        int index=0;
        String str;
        char output;

        System.out.print("Enter the String : ");
        str=strscan.next();
        System.out.print("Enter the Index : ");
        index=strscan.nextInt();

        output=str.charAt(index-1);
        System.out.print("The Letter in index ["+index+"]is : "+output);

    }

Compare Two Strings

 

public class stringcomp
{

    public static void main(String args[])
    {
        Scanner scan=new Scanner(System.in);
        String a="Test";
        String b="Test";
        int rep=0;

            System.out.println("Enter String 1 : ");
            a=scan.next();
            System.out.println("Enter String 2 : ");
            b=scan.next();
            rep=a.compareTo(b);

        if(rep==0)
        {
            System.out.println("String Matching");
        }
        else
        {
            System.out.println("String Not Matching");
        }

    }

}

Declare Variables

 

public class decver

{
        public static void main(String args[])
        {
            int i=5;
            float i1=0.5f
            byte b =1;
            char a='A';
            String ab ="Hello Java";
            boolean flag=true;
        }

Hello World Java

 

public class Basic
{
    public static void main (String args[])
    {
        System.out.println("Hello");
    }
}