Java Interview Questions

 


Java Interview Questions

In this tutorial we will see about some basic Java programming questions asked in interview. Below are the list of few questions and along with solution.

  • Reversing a String without reverse() function
  • Add numbers from the given input
  • Count no. of words in the line or paragraph
  • Find Armstrong number or not
  • Find Prime number or not

Reversing a String without reverse() function

public class StringReverse {
 
 public static void main(String[] args) {
  
  String str = "Java Discover";
  System.out.println("Input String : "+str);
  str = myReverseFunction(str);
  System.out.println("Reversed String : "+str);
 }
 
 /**
  * Need to reverse a String without reverse() function
  * @param str
  * @return
  */
 public static String myReverseFunction(String str){
  char[] chars = str.toCharArray();
  StringBuilder sb = new StringBuilder();
  for (int i=str.length()-1;i>=0;i--) {
   sb.append(chars[i]);
  }
  return sb.toString();
 }
}


OUTPUT:


Input String : Java Discover
Reversed String : revocsiD avaJ



Add numbers from the given input
 

public class AddNumerals {
 
 public static void main(String[] args) {
  int value = 1234;
  int output = addNumerals(value);
  System.out.println("INPUT : "+value);
  System.out.println("OUTPUT : "+output);
 }
 
 /**
  * Add numerals in the given param value
  * For example input=1234 then output should be 1+2+3+4=10
  * @param value
  * @return
  */
 public static int addNumerals(int value){
  int output = 0;
  while(value > 0){
   output += value%10;
   value = value/10;
  }  
  return output;
 }
}



OUTPUT:


INPUT : 1234
OUTPUT : 10




Count no. of words in the line or paragraph
 

public class CountWords {

 public static void main(String[] args) {
  String line = "The string tokenizer class allows an application to break a string into tokens";
  int noOfWords = countNoOfWordsInLine(line);
  System.out.println("Input : "+line);
  System.out.println("No Of Words : "+noOfWords);
 }
 
 /**
  * Count no. of words in a line or paragraph 
  * @param line
  * @return
  */
 public static int countNoOfWordsInLine(String line){
  int output = 0;
  StringTokenizer tok = new StringTokenizer(line);
  output = tok.countTokens();
  return output;
 }
}



OUTPUT:


Input : The string tokenizer class allows an application to break a string into tokens
No Of Words : 13




Find Armstrong number or not
 

public class ArmstrongOrNot {
 
 public static void main(String[] args) {
  long input = 54748;
  boolean flag = checkArmstringOrNot(input);
  if(flag){
   System.out.println(input+" is Armstrong number");
  }else{
   System.out.println(input+" is NOT Armstrong number");
  }  
 }
 
 /**
  * Check given number is Armstrong number or not
  * For example, 371 is an Armstrong number, since 3^3 + 7^3 + 1^3 = 371 
  * @param input
  * @return
  */
 public static boolean checkArmstringOrNot(long input){
  int output = 0;
  long tmp = input;
        int length = Long.toString(input).length();
        while(tmp != 0){
         long rem = tmp % 10;
            long tmp1 = 1;
            for(int i = 0; i < length ;i++){
             tmp1 *= rem;
            }
            output += tmp1;
            tmp = tmp/10;
        }
        if(input == output){
            return true;
        }
        return false;
 }
}



OUTPUT:


54748 is Armstrong number




Find Prime number or not
 

public class PrimeOrNot {

 public static void main(String[] args) {
  int input = 23;
  boolean flag = primeOrNot(input);
  if(flag){
   System.out.println(input+" is a Prime number");
  }else{
   System.out.println(input+" is NOT a Prime number");
  }
 }
 
 /**
  * Check whether given number is Prime or Not
  * @param input
  * @return
  */
 public static boolean primeOrNot(int input){
  for(int i=2;i<=input/2;i++){
   if(input%i == 0){
    return false;
   }
  }
  return true;
 }
}



OUTPUT:


23 is a Prime number




More questions will be added shortly. 



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