设计模式学习—策略模式(Strategy Design Pattern)

桃扇骨 2022-06-09 04:35 119阅读 0赞

# 一、我的理解 #

策略模式讲究为某个类的对象提供不同的初始化参数（策略），那么它在执行某一动作时会采用不同的方法（初始化参数中实现的实际方法体）

# 二、实现方式 #

面向接口编程，为某个类初始化时提供不同的实现了相同接口的类的实例对象，该类实际执行动作时执行的是初始化参数中实际实现的方法体

# 三、实例 #

![Center][]

###### Java实例 ######

Strategy接口：策略的抽象接口，统一策略的执行方法入口

package com.study.dp.strategy;
    
    public interface Strategy {
        
        public int doOperation(int num1, int num2);
    
    }

OperationAdd类：实际实现的策略一，加法

package com.study.dp.strategy;
    
    public class OperationAdd implements Strategy {
    
        @Override
        public int doOperation(int num1, int num2) {
            return num1+num2;
        }
    
    }

OperationSubstract类：实际实现的策略二，减法

package com.study.dp.strategy;
    
    public class OperationSubstract implements Strategy {
    
        @Override
        public int doOperation(int num1, int num2) {
            return num1-num2;
        }
    
    }

OperationMultiply类：实际实现的策略三，乘法

package com.study.dp.strategy;
    
    public class OperationMultiply implements Strategy {
    
        @Override
        public int doOperation(int num1, int num2) {
            return num1*num2;
        }
    
    }

Context类：策略的执行类，向其传入不同策略的实例，则会执行不同的策略

package com.study.dp.strategy;
    
    public class Context {
        
        private Strategy strategy;
    
        public Context(Strategy strategy) {
            super();
            this.strategy = strategy;
        }
        
        public int executeStrategy(int num1, int num2) {
            return strategy.doOperation(num1, num2);
        }
    
    }

Demo类：测试类

package com.study.dp.strategy;
    
    public class Demo {
        
        public static void main(String[] args) {
            Context context = new Context(new OperationAdd());
            System.out.println("10 + 5 = "+context.executeStrategy(10, 5));
    
            context = new Context(new OperationSubstract());
            System.out.println("10 - 5 = "+context.executeStrategy(10, 5));
            
            context = new Context(new OperationMultiply());
            System.out.println("10 * 5 = "+context.executeStrategy(10, 5));
        }
    
    }

# 四、应用场景 #

[Center]: /images/20220609/80e1e735747744a99bdc18599d348268.png