19 行为模式 － 状态（State）模式

1.用意

状态模式允许一个对象在其内部状态改变的时候改变其行为。这个对象看上去就像是改变了它的类一样。

2.类图

3.代码

/*
 * 环境角色
 */
public class Context {
	private State state;

	public void sampleOperation() {
		state.sampleOperation();
	}

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

/*
 * 抽象状态
 */
public interface State {
	void sampleOperation();
}


/*
 * 具体状态类A
 */
public class ConcreteStateA implements State {
	public void sampleOperation() {
		S.s("ConcreteState::A");
	}
}


/*
 * 具体状态类B
 */
public class ConcreteStateB implements State {
	public void sampleOperation() {
		S.s("ConcreteState::B");
	}
}


/*
 * 测试类
 */
public class Test {

	public static void main(String[] args) {
		Context c = new Context();
		c.setState(new ConcreteStateA());
		c.sampleOperation();
		c.setState(new ConcreteStateB());
		c.sampleOperation();
	}
}

 

z

1.用意

状态模式允许一个对象在其内部状态改变的时候改变其行为。这个对象看上去就像是改变了它的类一样。

2.类图

3.代码

/*
 * 环境角色
 */
public class Context {
	private State state;

	public void sampleOperation() {
		state.sampleOperation();
	}

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

/*
 * 抽象状态
 */
public interface State {
	void sampleOperation();
}


/*
 * 具体状态类A
 */
public class ConcreteStateA implements State {
	public void sampleOperation() {
		S.s("ConcreteState::A");
	}
}


/*
 * 具体状态类B
 */
public class ConcreteStateB implements State {
	public void sampleOperation() {
		S.s("ConcreteState::B");
	}
}


/*
 * 测试类
 */
public class Test {

	public static void main(String[] args) {
		Context c = new Context();
		c.setState(new ConcreteStateA());
		c.sampleOperation();
		c.setState(new ConcreteStateB());
		c.sampleOperation();
	}
}

 

z

1.用意

状态模式允许一个对象在其内部状态改变的时候改变其行为。这个对象看上去就像是改变了它的类一样。

2.类图

3.代码

/*
 * 环境角色
 */
public class Context {
	private State state;

	public void sampleOperation() {
		state.sampleOperation();
	}

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

/*
 * 抽象状态
 */
public interface State {
	void sampleOperation();
}


/*
 * 具体状态类A
 */
public class ConcreteStateA implements State {
	public void sampleOperation() {
		S.s("ConcreteState::A");
	}
}


/*
 * 具体状态类B
 */
public class ConcreteStateB implements State {
	public void sampleOperation() {
		S.s("ConcreteState::B");
	}
}


/*
 * 测试类
 */
public class Test {

	public static void main(String[] args) {
		Context c = new Context();
		c.setState(new ConcreteStateA());
		c.sampleOperation();
		c.setState(new ConcreteStateB());
		c.sampleOperation();
	}
}

 

z