정책 모드 예

/**
 * @author zhaojianbo
 *          ，             
 */
public interface IStrategy {
    //              
    void operate();
}

/**
 * @author zhaojianbo
 */
public class BackDoor implements IStrategy {
    @Override
    public void operate() {
        System.out.println("    1");
    }
}

/**
 * @author zhaojianbo
 */
public class GivenGreenLight implements IStrategy {
    @Override
    public void operate() {
        System.out.println("    2");
    }
}

/**
 * @author zhaojianbo
 */
public class BlockEnemy implements IStrategy{
    @Override
    public void operate() {
        System.out.println("    3");
    }
}

/**
 * @author zhaojianbo
 */
public class Context {
    private IStrategy iStrategy;

    public Context(IStrategy iStrategy) {
        this.iStrategy = iStrategy;
    }

    public void operate() {
        iStrategy.operate();
    }
}

/**
 * @author zhaojianbo
 */
public class ZhaoYun {
    public static void main(String[] args) {
        Context context;
        System.out.println("------1-----");
        context = new Context(new BackDoor());
        context.operate();
        System.out.println("------end------");
        System.out.println("------2-----");
        context = new Context(new GivenGreenLight());
        context.operate();
        System.out.println("------end---");
        context = new Context(new BlockEnemy());
        context.operate();
        System.out.println("------3---");
        System.out.println("------end-----");
    }
}