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# Java Program to Check Whether a Number can be Expressed as Sum of Two Prime Numbers

###### Tutorialsrack 11/07/2021 Java

In this Java program, you’ll learn how to check whether a number can be expressed as the sum of two prime numbers. In this program, we used the following Java basics such as `for` loop, `if...else` conditions, and `break` statements.

Here is the code of the program to check whether a number can be expressed as the sum of two prime numbers.

##### Program - Java Program to Check Whether a Number can be Expressed as Sum of Two Prime Numbers
``````//Java Program to Check Whether a Number can be Expressed as Sum of Two Prime Numbers

import java.util.Scanner;

public class JavaPrograms {

public static void main(String[] args) {

int number;

// create an object of Scanner class
Scanner sc = new Scanner(System.in);

// ask users to enter numbers
System.out.println("Enter a number: ");
number = sc.nextInt();

boolean flag = false;
for (int i = 2; i <= number / 2; ++i) {

// condition for i to be a prime number
if (checkPrime(i)) {

// condition for n-i to be a prime number
if (checkPrime(number - i)) {

System.out.printf("%d = %d + %d\n", number, i, number - i);
flag = true;
}

}
}

if (!flag) {
System.out.println(number + " cannot be expressed as the sum of two prime numbers.");
}else {
System.out.println(number + " is expressed as the sum of two prime numbers.");
}
sc.close();
}

// Function to check prime number
public static boolean checkPrime(int num) {
boolean isPrime = true;

for (int i = 2; i <= num / 2; ++i) {
if (num % i == 0) {
isPrime = false;
break;
}
}

return isPrime;
}
}
``````
##### Output

Enter a number:

24

24 = 5 + 19

24 = 7 + 17

24 = 11 + 13

24 is expressed as the sum of two prime numbers.

In the above program, we have created the `checkPrime()` method to check whether a number is prime or not. This method returns `true` if the passed number is prime.

Here, we have a number 24. The program tries to check if 24 can be represented as the sum of two prime numbers or not.

### Working of Program

• First, we run a `for` loop from `i = 2` to `number / 2`.
• Inside the `for` loop, we used two `if` statements. The first statement checks if `i` is a prime number or not.

If it return `true`, the second if statement checks if the `number - i` is a prime number or not. This is because the sum of `i` and `number - i` is equal to the number.
• If the second statement is also `true`, then we can say the number 24 is a valid sum of two prime numbers.