//Strategy

abstract class Strategy {

public abstract void method();

}

//ConcreteStrategy

class strategyImplA extends Strategy {

public void method() {

System.out.println("这是第一个实现");

}

}

class StrategyImplB extends Strategy {

public void method() {

System.out.println("这是第二个实现");

}

}

class StrategyImplC extends Strategy {

public void method() {

System.out.println("这是第三个实现");

}

}

//Context

class Context {

Strategy stra;

public Context(Strategy stra) {

this.stra = stra;

}

public void doMethod() {

stra.method();

}

}

public class DS20_Stategy {

public static void main(String[] args) {

Context ctx = new Context(new strategyImplA());

ctx.doMethod();

ctx = new Context(new StrategyImplB());

ctx.doMethod();

ctx = new Context(new StrategyImplC());

ctx.doMethod();

}

}