Java Programming Interview Questions And Answers

Q1. How to reverse a String in java?

Solution:-

import java.util.Scanner;

public class ReverseString {


public static void main(String[] args)
{

String input="";
System.out.println("Enter the input String");

Scanner in = new Scanner(System.in);
input = in.nextLine();
char[] chr=input.toCharArray();
for(int i=chr.length-1; i>=0; i--)

System.out.print(chr[i]);
}

}

Output:-
Enter the input String
Ankit
tiknA


Q2. How to find the first non repeated character in the String?

Soution:-

import java.util.HashMap;
import java.util.Scanner;


public class FirstNonRepated {


    
    public static void main(String[] args)
    {
        // TODO Auto-generated method stub
        
        System.out.println(" Please enter the input string :" );
        Scanner in = new Scanner (System.in);
        String s=in.nextLine();
        char c=firstNonRepeatedCharacter(s);
        System.out.println("The first non repeated character is :  " + c);
    }
    
    public static Character firstNonRepeatedCharacter(String str)
    {
        HashMap<Character,Integer>  characterhashtable= 
                     new HashMap<Character ,Integer>();
        int i,length ;
        Character c ;
        length= str.length(); 
        for (i=0;i < length;i++)
        {
            c=str.charAt(i);
            if(characterhashtable.containsKey(c))
            {
                // increment count corresponding to c
                characterhashtable.put(  c ,  characterhashtable.get(c) +1 );
            }
            else
            {
                characterhashtable.put( c , 1 ) ;
            }
        }
      
        
        for (i =0;i < length;i++ )
        {
            c= str.charAt(i);
            if( characterhashtable.get(c)  == 1 )
            return c;
        }
        return null ;
    }

} 

OutPut:-

 Please enter the input string :
 Ankit

The first non repeated character is :  A