定義
當(dāng)一個(gè)對(duì)象的內(nèi)在狀態(tài)改變時(shí)允許改變其行為酥泛，這個(gè)對(duì)象看起來(lái)像是改變了其類
public interface TvState {
public void next();
public void pre();
public void up();
public void down();
}
package com.qc.state;
public class PowerOffState implements TvState {
@Override
public void next() {
// TODO Auto-generated method stub
}
@Override
public void pre() {
// TODO Auto-generated method stub
}
@Override
public void up() {
// TODO Auto-generated method stub
}
@Override
public void down() {
// TODO Auto-generated method stub
}
}
package com.qc.state;
public class PowerOnState implements TvState {
@Override
public void next() {
// TODO Auto-generated method stub
System.out.println("下一首");
}
@Override
public void pre() {
// TODO Auto-generated method stub
System.out.println("上一首");
}
@Override
public void up() {
// TODO Auto-generated method stub
System.out.println("上");
}
@Override
public void down() {
// TODO Auto-generated method stub
System.out.println("下");
}
}
package com.qc.state;
public interface PowerController {
public void powerOn();
public void powerOff();
}
package com.qc.state;
public class Tv implements PowerController {
TvState mTvState;
@Override
public void powerOn() {
// TODO Auto-generated method stub
setTvState(new PowerOnState());
}
@Override
public void powerOff() {
// TODO Auto-generated method stub
setTvState(new PowerOffState());
}
public void setTvState(TvState mTvState) {
this.mTvState = mTvState;
}
public void next() {
mTvState.next();
}
public void pre() {
mTvState.pre();
}
public void up() {
mTvState.up();
}
public void down() {
mTvState.down();
}
}
package com.qc.state;
public class Client {
public static void main(String[] args) {
// TODO Auto-generated method stub
Tv mTv = new Tv();
mTv.powerOn();
mTv.next();
mTv.pre();
mTv.up();
mTv.down();
}
}
使用
1惠毁、一個(gè)對(duì)象的行為取決于它的狀態(tài)郑临。并且它必須在運(yùn)行時(shí)根據(jù)狀態(tài)改變它的行為据过。
2、代碼中包含大量與對(duì)象狀態(tài)有關(guān)的條件語(yǔ)句妒挎，例如绳锅，一個(gè)操作中含有龐大的多分支語(yǔ)句（if-else或switch-case），且這些分支依賴于該對(duì)象的狀態(tài)酝掩。
