00:00

Help Us Improve

We're sorry this tutorial wasn't helpful. Please tell us what we can do better.

Java Program to Add Two Numbers

Last updated:

Adding two numbers is one of the first programs every Java learner writes. It shows how to declare variables, use the + operator and print the result.

1. Add Two Numbers with Fixed Values

The program adds two whole numbers stored in int variables and two decimal numbers stored in double variables.

AddTwoNumbers.java 
public class AddTwoNumbers {
    public static void main(String[] args) {
        int a = 20;
        int b = 40;
        int sum = a + b;
        System.out.println(a + " + " + b + " = " + sum);

        double x = 10.5;
        double y = 20.75;
        System.out.println(x + " + " + y + " = " + (x + y));
    }
}
Output
20 + 40 = 60
10.5 + 20.75 = 31.25
Note: the brackets in (x + y) matter. Without them, Java would join the text and the numbers from left to right and print 10.520.75 instead of adding them.

2. Add Two Numbers with User Input

The Scanner class reads the numbers from the keyboard. nextDouble() accepts both whole and decimal numbers.

AddTwoNumbersInput.java 
import java.util.Scanner;

public class AddTwoNumbersInput {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter first number: ");
        double first = scanner.nextDouble();
        System.out.print("Enter second number: ");
        double second = scanner.nextDouble();
        scanner.close();

        double sum = first + second;
        System.out.println("Sum: " + sum);
    }
}
Output (with sample input)
Enter first number: 55.50
Enter second number: 20.40
Sum: 75.9

Decimal arithmetic in binary can show tiny rounding errors, such as 0.1 + 0.2 printing 0.30000000000000004. Use printf("%.2f", sum) to round the output, or BigDecimal for exact values.

3. Add Two Numbers Using a Method

Putting the addition in a method makes it reusable. The long version shows why the type matters: adding two large int values overflows, while long holds the correct result.

AddWithMethod.java 
public class AddWithMethod {

    static int add(int a, int b) {
        return a + b;
    }

    static long add(long a, long b) {
        return a + b;
    }

    public static void main(String[] args) {
        System.out.println("15 + 27 = " + add(15, 27));

        int big = 2_000_000_000;
        System.out.println("int:  " + big + " + " + big + " = " + add(big, big));
        System.out.println("long: " + big + " + " + big + " = " + add((long) big, (long) big));
    }
}
Output
15 + 27 = 42
int:  2000000000 + 2000000000 = -294967296
long: 2000000000 + 2000000000 = 4000000000

4. Summary

  • Use the + operator to add two numbers, and wrap the sum in brackets when printing it with text.
  • Read numbers from the user with Scanner.nextInt() or nextDouble().
  • int overflows above about 2.1 billion; use long for larger sums.
  • Use printf() or BigDecimal when decimal results must look exact.

Related Programs