Allow an object to alter its behavior when its internal state changes.The object will appear to change its class.(当一个对象内在状态改变时,允许其改变行为,这个对象看起来像改变了其类)
状态模式适应
public abstract class LiftState {
protected Context context;
public void setContext(Context _context){
this.context=_context;
}
public abstract void open();
public abstract void close();
public abstract void run();
public abstract void stop();
}
关闭状态
public class ClosingState extends LiftState {
@Override
public void close() {
System.out.println("close the lift");
}
@Override
public void open() {
super.context.setLiftState(Context.openningState);
super.context.getLiftState().open();
}
@Override
public void run() {
super.context.setLiftState(Context.runningState);
super.context.getLiftState().run();
}
@Override
public void stop() {
super.context.setLiftState(Context.stoppingState);
super.context.getLiftState().stop();
}
}
停止状态public class StoppingState extends LiftState {
@Override
public void close() {
//do nothing
}
@Override
public void open() {
super.context.setLiftState(Context.openningState);
super.context.getLiftState().open();
}
@Override
public void run() {
super.context.setLiftState(Context.runningState);
super.context.getLiftState().run();
}
@Override
public void stop() {
System.out.println("the lift is stoped");
}
}
运行状态public class RunningState extends LiftState {
@Override
public void close() {
//do nothing
}
@Override
public void open() {
//do nothing
}
@Override
public void run() {
System.out.println("lift is runing...");
}
@Override
public void stop() {
super.context.setLiftState(Context.stoppingState);
super.context.getLiftState().stop();
}
}
开门状态public class OpenningState extends LiftState {
@Override
public void close() {
super.context.setLiftState(Context.closingState); //调用的是Context中的方法
super.context.getLiftState().close(); //通过Context调用另一个状态的方法
}
@Override
public void open() {
System.out.println("lift is open...");
}
@Override
public void run() {
//do nothing
}
@Override
public void stop() {
//do nothing
}
}
上下文对象public class Context {
public final static OpenningState openningState=new OpenningState();
public final static ClosingState closingState=new ClosingState();
public final static RunningState runningState=new RunningState();
public final static StoppingState stoppingState=new StoppingState();
private LiftState liftState;
public LiftState getLiftState() {
return liftState;
}
public void setLiftState(LiftState liftState) {
this.liftState = liftState;
this.liftState.setContext(this); //将该状态设置上下文对象
}
public void close() {
this.liftState.close();
}
public void open() {
this.liftState.open();
}
public void run() {
this.liftState.run();
}
public void stop() {
this.liftState.stop();
}
}
场景测试
public class Client {
public static void main(String[] args) {
Context context=new Context();
context.setLiftState(Context.closingState);
context.open();
context.close();
context.run();
context.stop();
}
}
/*
上下文对象Context,成员属性LiftState,可设置四种状态,获取和改变状态,相当于一个公共容器
四种状态的抽象LiftState,成员属性Context,可设置上下文对象,让四种状态都拥有同一个Context
你中有我,我中有你,通过容器Context可以进行状态的切换,将四者联合成一体
当状态改变时,通过父类的统一Context改变了LiftState状态,然后调用了改变后状态的方法
也就是说
*/
结果
lift is open...
close the lift
lift is runing...
the lift is stoped
我是菜鸟,我在路上。