# Strategy

Paul Tomoiu

●

Examples,

Design patterns

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Published 2022-12-03

This tutorial explains to you the design pattern named Strategy (which is a Structural Pattern).

# Strategy Pattern - theory

Strategy Design Pattern in Java is used when we want to adopt a strategy function of context. This pattern makes the Java application easier to extend and incorporate new behaviors. The Strategy Pattern is also known as Policy.

Take a look at the following UML diagram representing the Strategy design pattern (for my example):

# Strategy Pattern - example

Here is an example of using the Strategy Design Pattern in Java:

package strategy.java.pattern.example;
 
public interface ToDo {
 
    public void enjoy();
 
}

package strategy.java.pattern.example;
 
public class IsWinter implements ToDo {
 
    @Override
    public void enjoy() {
        System.out.println("You GO SKIING.");
        System.out.println("You BUILD a SNOWMAN."); 
    }
}

package strategy.java.pattern.example;
 
public class IsSummer implements ToDo {
 
    @Override
    public void enjoy() {
        System.out.println("You GO SWIMMING.");
        System.out.println("You PLAY SOCCER."); 
    }
}

package strategy.java.pattern.example;
 
public class Context {
 
    private ToDo toDo;
 
    public Context(ToDo toDo){
       this.toDo = toDo;
    }
 
    public void contextEnjoy(){
       toDo.enjoy();
    }
}

package strategy.java.pattern.example;
 
public class StrategyJavaPatternExample {
 
    public static void main(String[] args) {
         
        ToDo winter = new IsWinter();
        Context context1 = new Context(winter);
        context1.contextEnjoy();
         
        System.out.println("");
         
        ToDo summer = new IsSummer();
        Context context2 = new Context(summer);
        context2.contextEnjoy();
    }
}

When you run this example you will receive the following result: