How to Use Strategy Pattern in Java

In this example, we can learn how to implement Strategy Pattern in Java.

Source Code

1)

package com.beginner.examples;

public interface Strategy1 {
	   //define operation name
	   public int operation(int num1, int num2);
	}

2)

package com.beginner.examples;

public class Strategy2 implements Strategy1{
	   @Override
	   public int operation(int num1, int num2) {
		  // add
	      return num1 + num2;
	   }
	}

3)

package com.beginner.examples;

public class Strategy3 implements Strategy1{
	   @Override
	   public int operation(int num1, int num2) {
		  // substract
	      return num1 - num2;
	   }
	}

4)

package com.beginner.examples;

public class Strategy4 {
	   private Strategy1 strategy;
	 
	   public Strategy4(Strategy1 strategy){
	      this.strategy = strategy;
	   }
	   // execute strategy
	   public int execute(int num1, int num2){
	      return strategy.operation(num1, num2);
	   }
	}

5)

package com.beginner.examples;

public class StrategyExample {
	   public static void main(String[] args) {
		  // execute add operation
		  Strategy4 s = new Strategy4(new Strategy2());    
	      System.out.println("6 + 1 = " + s.execute(6, 1));
	      // execute substract operation
	      s = new Strategy4(new Strategy3());      
	      System.out.println("6 - 1 = " + s.execute(6, 1));
	   }
	}

Output:

6 + 1 = 7
6 - 1 = 5