状态模式

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状态模式(State):当一个对象的内在状态改变时允许改变其行为，这个对象看起来像是改变了一个类

Class Diagram

Implementation

状态接口

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public abstract class State {
    protected String desc;
    public abstract void handle(Context context);
    public abstract void display();
}

具体状态

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public class ConcreteStateA extends State {

    {
        desc = "休息中";
    }

    @Override
    public void handle(Context context) {
        System.out.println("当前状态" + desc);
        System.out.println("状态处理，切换工作状态");
        context.setState(new ConcreteStateB());
    }

    @Override
    public void display() {
        System.out.println("状态:" + desc);
    }
}

public class ConcreteStateB extends State {

    {
        desc = "工作中";
    }

    @Override
    public void handle(Context context) {
        System.out.println("当前状态" + desc);
        System.out.println("状态处理，切换工作状态");
        context.setState(new ConcreteStateA());
    }

    @Override
    public void display() {
        System.out.println("状态:" + desc);
    }
}

使用状态的实例

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public class Context {
    private State state;

    public Context(State state) {
        this.state = state;
    }

    public State getState() {
        return state;
    }

    public void setState(State state) {
        this.state = state;
    }

    public void request(){
        state.handle(this);
    }

    public void displayState(){
        state.display();
    }
}

测试类

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public class StateTest {
    @Test
    public void test() throws Exception {
        Context context = new Context(new ConcreteStateA());
        context.displayState();
        context.request();
        context.displayState();
        context.request();
        context.displayState();
    }
}

Example

Reflence