Java设计模式之策略模式原理与用法实例详解

package com.test;
/**
 * 策略模式抽象角色
 * @author zhouwen
 *
 */
public interface Strategy {
  public int calculate(int a, int b);
}

package com.test;
/**
 * 策略模式具体策略类
 * 实现加法运算
 * @author zhouwen
 *
 */
public class AddStrategy implements Strategy {
  @Override
  public int calculate(int a, int b) {
    return a + b;
  }
}

package com.test;
/**
 * 策略模式具体策略类
 * 实现减法运算
 * @author zhouwen
 *
 */
public class SubtractStrategy implements Strategy {
  @Override
  public int calculate(int a, int b) {
    return a - b;
  }
}

package com.test;
/**
 * 策略模式具体策略类
 * 实现乘法运算
 * @author zhouwen
 *
 */
public class MultiplyStragety implements Strategy {
  @Override
  public int calculate(int a, int b) {
    return a * b;
  }
}

package com.test;
/**
 * 策略模式具体策略类
 * 实现除法运算
 * @author zhouwen
 *
 */
public class DivideStrategy implements Strategy {
  @Override
  public int calculate(int a, int b) {
    return a / b;
  }
}

package com.test;
/**
 * 策略模式环境类
 * @author zhouwen
 *
 */
public class Environment {
  private Strategy strategy;
  public Environment(Strategy strategy){
    this.strategy = strategy;
  }
  //用以改变策略
  public void setStrategy(Strategy strategy){
    this.strategy = strategy;
  }
  public Strategy getStrategy(){
    return strategy;
  }
  //暴露计算的接口，供客户端调用
  public int calculate(int a, int b){
    return strategy.calculate(a, b);
  }
}

package com.test;
public class Client {
  public static void main(String[] args) {
    AddStrategy addStrategy = new AddStrategy();
    Environment environment = new Environment(addStrategy);
    System.out.println(environment.calculate(3, 4));
    SubtractStrategy subStrategy = new SubtractStrategy();
    environment.setStrategy(subStrategy);
    System.out.println(environment.calculate(3, 4));
    MultiplyStragety multiplyStrategy = new MultiplyStragety();
    environment.setStrategy(multiplyStrategy);
    System.out.println(environment.calculate(3, 4));
    DivideStrategy divideStrategy = new DivideStrategy();
    environment.setStrategy(divideStrategy);
    System.out.println(environment.calculate(3, 4));
  }
}