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Java Programming Questions and Answers

Java Programming Questions and Answers: we have listed some most important Java Programming Questions and Answers frequently asked in written test of Java.
Q:- Write a program to print "Hello World" in Java
public class PrintMessage {
    public static void main(String[] args) {
      System.out.println("Hello World");
   }
}

//Output: Hello World
Q:- Write a program to print "Hello World" without using main method in Java
public class PrintMessage {
    static {
        System.out.println("Hello World");
        System.exit(0);
    } 
}

//Note - 
//1. The System.exit(0) exits the program before the JVM starts to look for main()
//2. This will not work with JDK7 - Because, In JDK7 the code would not execute as it looks for the main method before any other thing.

//Output: Hello World
Q:- Write a factorial program using recursion in Java
public class Factorial {  
 static int calFactorial(int n){    
  if (n == 0){
    return 1; 
  }else {
    return(n * calFactorial(n-1));   
  }    
 }    
 public static void main(String args[]){    
  int number = 5; 
  int factOutput = 1;  
  factOutput = calFactorial(number);   
  System.out.println("Factorial of the number "+number+" is: "+factOutput);    
 }  
}  

//Output: Factorial of the number 5 is: 120
Q:- Write a program to sum of two numbers in Java
public class SumClass {
    public static void main(String args[]) {
        int x=10;
        int y=20;
        int z=x+y;
        System.out.println("Sum of x+y = " + z);
    }
}


//Output: Sum of x+y = 30
Q:- Write a program to check whether the given number is even or odd in Java
import java.util.Scanner;
public class CheckNumberEvenOdd {
    public static void main(String[] args) {
        Scanner reader = new Scanner(System.in);
        System.out.print("Enter your number: ");
        int num = reader.nextInt();
        if(num % 2 == 0)
            System.out.println(num + " is an even number.");
        else
            System.out.println(num + " is an odd number.");
    }
}

//Note - Scanner object, reader is created to read a number from the user's keyboard. 
Q:- Write a program to print fibonacci series based on the user input in Java
import java.util.Scanner;
public class FibonacciSeries {
    public static void main(String[] args) {
        int count, num1 = 0, num2 = 1;
        System.out.println("How many numbers you want in the series:");
        Scanner scanner = new Scanner(System.in);
        count = scanner.nextInt();
        scanner.close();
        System.out.print("Fibonacci Series of "+count+" numbers:");
        int i=1;
        while(i<=count){
            System.out.print(num1+" ");
            int sumOfPrevTwo = num1 + num2;
            num1 = num2;
            num2 = sumOfPrevTwo;
            i++;
        }
    }
}

//Output - Fibonacci Series of 10 numbers:0 1 1 2 3 5 8 13 21 34 
OR
public class FibonacciSeries {
 public static void main(String args[]) {
  int n1 = 0, n2 = 1, no, i, count = 10;
  System.out.print("Fibonacci Series of " + count + " numbers:" + n1 + " " + n2);
  for (i = 2; i <
   count; ++i) {
   no = n1 + n2;
   System.out.print(" " + no);
   n1 = n2;
   n2 = no;
  }
 }
}
//Output - Fibonacci Series of 10 numbers:0 1 1 2 3 5 8 13 21 34
Some other important questions are:
Q:- Write a program to swap two numbers without using 3rd variable in Java.
Q:- Write a program to get the prime numbers between a given range in Java.
Q:- Write a program to check whether a number is prime or not in Java.
Q:- Write a program to check whether a number is armstrong or not in Java.
Q:- Write a program to check whether a string is palindrome or not in Java.
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