How to Subtract Two Numbers in Java Using a For Loop

Performing basic arithmetic operations is a fundamental part of learning any programming language, including Java. In this tutorial, we’ll walk through how to create a simple Java program that subtracts two numbers using a for loop. While subtraction is typically a straightforward operation, using a loop introduces a slightly different approach that helps reinforce the use of iterative logic in Java. Whether you’re a beginner or brushing up on your Java skills, this example will help you understand how control structures like loops can be used creatively for basic tasks.

How to Subtract Two Numbers in Java

Using a for loop.

Program 1

// subtract two numbers
//using a for loop
class Subtract_With_Forloop {
    public static void main(String[] args) {
        int num1=100;
         int num2=50;
         int result=0;
         //subtracting number 2 from number 1 using for loop
                for(int i=0; i<num2; i++){
result--;
}
System.out.println("result of subtraction: ");
System.out.println(num1 + "-" + num2 + "=" + result);
        
    }
}

When the above code is executed, it produces the following result

result of subtraction:
100-50=-50

Explanation

This Java program subtracts one number (num2) from another (num1) using a for loop.

Here’s what’s happening step-by-step:

1. Two integers are declared:

num1=100;

num2=50;

2. A variable result is initialized to 0.

3. A for loop runs num2 times (in this case, 50 times).

4. Each time the loop runs, it decreases the value of result by 1 (result–).

5. So after 50 iterations, result becomes -50.

6. Finally, it prints the subtraction result as:

100-50=50

Using a for loop and a method

Program 2

//Calculate subtraction of two numbers using a for loop with method
class Subtraction_Twonum_UsingLoop {
    public static void main(String[] args) {
         int result;
        int num_1=150;
         int num_2=25;
          result=subtractForMethod(num_1,num_2);

        System.out.println(num_1+" and " - "+ " + num_2 + " is =" + result);
    }
    
public static int subtractForMethod(int a, int b){
    int result=a;
         for(int i=0; i<b; i++){
result--;

}
return result;
        
}
}

When the above code is executed, it produces the following result

output :

150 and -25 is=125

Explanation

This program subtracts two numbers using a for loop and a method in Java.

Step-by-step breakdown:

1. Inside the main method:

   • Two numbers are defined:

num_1=150

num_2=25

1. • The program calls the method subtractForMethod(num_1,num_2), num_2) to do the subtraction.

   • The result is then printed.

2. The subtractForMethod method does the actual subtraction:

   • It starts with result=a (which is num_1)

   • It runs a for loop b times (which is num_2)

   • In each loop, it decreases result by 1
     So it’s like doing: a – 1 – 1 – 1….. (25 times)

3. After the loop, the final result is returned to the main method and printed.

Using a for loop, and the Scanner class.

Program 3

//subtract two numbers using a loop
import java.util.Scanner;
class Subtraction_Twonum_UsingLoop {
    public static void main(String[] args) {
Scanner input=new Scanner(System.in);
 System.out.println("Input value for num1:");
         
int num1=input.nextInt();

 System.out.println("Input value for num2:");
         
int num2=input.nextInt();
             System.out.println("Subtraction of two numbers using a for loop:");
       int result=num1;
                for(int i=0; i<num2; i++){
result--;
}
System.out.println(num1 + "+" + num2 + "=" + result);

    }
}

When the above code is executed, it produces the following result

Input value for num1:
35
Input value for num2:
20
Subtraction of two numbers using a for loop:
35+20=15

Explanation

This Java program subtracts two numbers using a for loop, and it lets the user enter the numbers using the Scanner class.

Step-by-step breakdown:

1. User Input:

   • The program asks the user to enter two numbers:

     num1 (the number to subtract from

   • num2 (the number to subtract)

2. Subtraction Logic:

   • It starts by setting result = num1

   • Then, a for loop runs num2 times

   • In each loop, result is decreased by 1 (result–)

   • So the loop is subtracting 1 repeatedly,  num2 times

3. Output:

   • It prints the subtraction result
     ⚠️ However, there’s a mistake in the output line:
     System.out.println(num1 + "+" + num2 + "=" + result);
     This line wrongly shows a plus "+" sign instead of a minus "-".

Using a loop inside a method

Program 4

//subtract two numbers using a loop
import java.util.Scanner;
class Subtraction_Twonum_UsingLoop {
    public static void main(String[] args) {
Scanner input=new Scanner(System.in);
 System.out.println("Input value for num1:");
         
int num1=input.nextInt();

 System.out.println("Input value for num2:");
         
int num2=input.nextInt();
          int result=subtractForMethod(num1,num2);
    System.out.println("Subtraction of two numbers using a loop:");
       System.out.println(num1 + "-" + num2 + "=" + result);
        
    }
    
        public static int subtractForMethod(int a, int b){
    int result=a;
         for(int i=0; i<b; i++){
result--;

}
return result;
}
}

When the above code is executed, it produces the following result

Input value for num1:
100
Input value for num2:
10
Subtraction of two numbers using a loop:
100-10=90

Explanation

This Java program subtracts two numbers using a loop inside a method, and it takes input from the user.

Step-by-step Breakdown:

1. User Input:

The program uses the Scanner class to take two numbers from the user:

• num1- the number to subtract from
• num2 – the number to subtract

1. Calling a Method:

   • The program calls a method named subtractForMethod(num1, num2) to perform the subtraction.

2. Subtraction Using a Loop:

   • Inside the method:

     • It sets result = a (starting with the first number)

     • Then, it runs a for loop b times

     • Each time, it decreases result by 1 (result–)

     • So it’s like doing: a – -1 – 1 – 1….  repeated b times

3. Final Output:

   • After the loop finishes, the method returns the result.

   • The main method prints the final subtraction result in the format:
     num1 – num2=result

Example:

If the user enters:

• num1=100;
• num2=30

Then the loop will subtract 1 from 100 a total of 30 times.
The result will be 70, and the output will be:

Related post

10 ways to add two numbers in Java

20 ways to subtract two numbers in Java

Subtraction of two numbers in Java using recursion 

Subtraction of two numbers in PHP

Addition of two numbers using pascal in various ways

Pascal Code for Subtracting Two Numbers Using Various Methods