state-----设计模式

1.状态模式，当我们处理一些情况是，要依据别人对象的状态来决定处理的内容，我们呢可以 为不同的状态生成不同的类，在核心类中，我们就可以依据不同的状态来得到不同的处理。

2.一个较为复杂的示例：

package com.cn;import java.awt.BorderLayout;import java.awt.Button;import java.awt.Color;import java.awt.Frame;import java.awt.Panel;import java.awt.TextArea;import java.awt.TextField;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import java.util.HashSet;interface Context {public abstract void setClock(int hour);public abstract void changeState(State state);public abstract void callSecurityCenter(String msg);public abstract void recordLog(String msg);}interface State {public abstract void doClock(Context context, int hour);public abstract void doUse(Context context);public abstract void doAlarm(Context context);public abstract void doPhone(Context context);}class DayState implements State {private static DayState singleton = new DayState();private DayState(){}public static State getInstance() {return singleton;}public void doClock(Context context, int hour) {if (hour < 9 || 17 <= hour) {context.changeState(NightState.getInstance());}}public void doUse(Context context) {context.recordLog("使用金库(白天)");}public void doAlarm(Context context) {context.recordLog("警铃(白天)");}public void doPhone(Context context) {context.callSecurityCenter("一般的通话(白天)");}public String toString() {return "【白天】";}}class NightState implements State {private static NightState singleton = new NightState();private NightState(){}public static State getInstance() {return singleton;}public void doClock(Context context, int hour) {if (hour >= 9 &&17 > hour) {context.changeState(DayState.getInstance());}}public void doUse(Context context) {context.recordLog("异常：晚间使用金库！");}public void doAlarm(Context context) {context.recordLog("警铃(晚间)");}public void doPhone(Context context) {context.callSecurityCenter("晚间的通话录音");}public String toString() {return "【晚间】";}}class SafeFrame extends Frame implements ActionListener ,Context {private TextField textClock = new TextField(60);private TextArea textScreen = new TextArea(10, 60);private Button buttonUse = new Button("使用金库");private Button buttonAlarm = new Button("警铃");private Button buttonPhone = new Button("一般通话");private Button buttonExit = new Button("结束");private State state = DayState.getInstance();public SafeFrame(String title) {super(title);setBackground(Color.lightGray);setLayout(new BorderLayout());add(textClock, BorderLayout.NORTH);textClock.setEditable(false);add(textScreen, BorderLayout.CENTER);textScreen.setEditable(false);Panel panel = new Panel();panel.add(buttonUse);panel.add(buttonAlarm);panel.add(buttonPhone);panel.add(buttonExit);add(panel, BorderLayout.SOUTH);pack();setVisible(true);buttonUse.addActionListener(this);buttonAlarm.addActionListener(this);buttonPhone.addActionListener(this);buttonExit.addActionListener(this);}public void actionPerformed(ActionEvent e) {System.out.println("" + e);if (e.getSource() == buttonUse) {state.doUse(this);} else if (e.getSource() == buttonAlarm) {state.doAlarm(this);} else if (e.getSource() == buttonPhone) {state.doPhone(this);} else if (e.getSource() == buttonExit) {System.exit(0);} else {System.out.println("?");}}public void setClock(int hour) {String clockstring = "现在的时间是：";if (hour < 10) {clockstring += "0" + hour + ":00";} else {clockstring += hour + ":00";}System.out.println(clockstring);textClock.setText(clockstring);state.doClock(this, hour);}public void changeState(State state) {System.out.println("状态已经从" + this.state + "变成" + state + "。");this.state = state;}public void callSecurityCenter(String msg) {textScreen.append("call!" + msg + "\n");}public void recordLog(String msg) {textScreen.append("record..." + msg + "\n");}}public class Main {public static void main(String[] args) {SafeFrame frame = new SafeFrame("State Sample");HashSet<Integer> set =  new HashSet<Integer>();set.add(4);System.out.println(set.size());while (true) {for (int hour = 0; hour < 24; hour ++) {frame.setClock(hour);try {Thread.sleep(1000);} catch (Exception e) {// TODO: handle exception}}}}}