Strategy design pattern design model ---

Strategy Mode

1) basic definition

A class act or algorithm can be changed at run time, it is a pattern of behavior.
Intent: define a series of algorithms, encapsulate them, and make them interchangeable.
To solve the problem: Under a variety of algorithms similar case, if ... else brought complex and difficult to maintain
usage scenarios: a system has more than one class, and differentiate their direct their behavior just
how to solve: Scene represent respective strategies objects and object change a behavior change strategy as the context object policy object change point arithmetic context object.
The key code: implement the same interface

Class Diagram:

 

2.demo Code:

Policy Interface:

public interface Strategy {
    public int doOperation(int num1,int num2);
}

Strategy interface class:

public class StrategyAdd implements Strategy{
    @Override
    public int doOperation(int num1, int num2) {
        return num1 + num2;
    }
}

public class StrategyMultiply implements Strategy{
    @Override
    public int doOperation(int num1, int num2) {
        return num1 * num2;
    }
}

Policy Context:

public class StrategyContex {
    Strategy strategy;
    public StrategyContex(Strategy strategy) {
        this.strategy = strategy;
    }
    public void setStrategy(Strategy strategy) {
        this.strategy = strategy;
    }
    public int executeStrategy(int num1,int num2) {
        return strategy.doOperation(num1, num2);
    }
}

Call demo:

public class StrategyDemo {
    public static void main(String[] args) {
        int num1 = 2,num2 = 3;
        StrategyContex contextAdd = new StrategyContex(new StrategyAdd());
        System.out.println(contextAdd.executeStrategy(num1, num2));
        
        StrategyContex contextMultiply = new StrategyContex(new StrategyMultiply());
        System.out.println(contextMultiply.executeStrategy(num1, num2));
        
        System.out.println("*************");
        contextMultiply.setStrategy(new StrategyAdd());
        System.out.println(contextMultiply.executeStrategy(num1, num2));
    }
}

Call demo output: