How to implement Loosely Coupled Application in Java?

Loose coupling is a design principle that promotes the independence of components in a software system. In Java, there are several ways to achieve loose coupling, but one of the most common is through the use of interfaces. By programming to an interface rather than a concrete implementation, components can be easily swapped out and replaced without affecting the rest of the system. Here’s an example of how to implement a loosely coupled application in Java using interfaces:

public interface Operation {
  int perform(int a, int b);
}

public class Addition implements Operation {
  @Override
  public int perform(int a, int b) {
    return a + b;
  }
}

public class Multiplication implements Operation {
  @Override
  public int perform(int a, int b) {
    return a * b;
  }
}

public class Calculator {
  private final Operation operation;

  public Calculator(Operation operation) {
    this.operation = operation;
  }

  public int calculate(int a, int b) {
    return operation.perform(a, b);
  }
}

public class Main {
  public static void main(String[] args) {
    Operation addition = new Addition();
    Calculator calculator = new Calculator(addition);
    int result = calculator.calculate(2, 3);
    System.out.println("Result of 2 + 3 using addition: " + result);

    Operation multiplication = new Multiplication();
    calculator = new Calculator(multiplication);
    result = calculator.calculate(2, 3);
    System.out.println("Result of 2 * 3 using multiplication: " + result);
  }
}