状态模式

一、前言

  允许一个对象的内部状态改变时改变它的行为。对象看起来似乎修改了它的类。

二、结构图

  

 三、应用场景

  ◆ 在Context 中进行状态的维护和转换

 public interface VoteState {

          /**
           * 处理状态对应的行为
           * @param user 投票人
           * @param voteItem 投票项
           * @param manager 投票上下文，用来实现状态对应的功能处理的时候，可以回调上下文的数据
           */
           public void vote(String user, String voteItem, VoteManager manager);
}

public class NormalVoteState implements VoteState {

          @Override
          public void vote(String user, String voteItem, VoteManager manager) {
                    manager.getMapVote().put(user, voteItem);
                    System.out.println("恭喜你投票成功！");
          }
}

public class RepeatVoteState implements VoteState {

        @Override
         public void vote(String user, String voteItem, VoteManager manager) {
                   System.out.println("请不要重复投票！");
         }
}

public class SpiteVoteState implements VoteState {

          @Override
          public void vote(String user, String voteItem, VoteManager manager) {
                    String s = manager.getMapVote().get(user);
                    if(s != null){
                             manager.getMapVote().remove(user);
                    }
                    System.out.println("你有恶意刷票行为，取消投票资格。");
          }
}

public class BlackVoteState implements VoteState {

          @Override
          public void vote(String user, String voteItem, VoteManager manager) {
                    System.out.println("进入黑名单，将禁止登陆和使用本系统。");
          }
}

public class VoteManager {

          /**
           * 持有状态处理对象
           */
          private VoteState state = null;
          /**
           * 记录用户投票的结果，Map<String,String>对应Map<用户名，投票的选项>
           */
          private Map<String, String> mapVote = new HashMap<String, String>();
          /**
           * 记录用户投票次数，Map<String,Integer> 对应Map<用户名，投票的次数>
           */
          private Map<String, Integer> mapVoteCount = new HashMap<String, Integer>();
          /**
           * 获取记录用户投票结果的Map
           * @return 记录用户投票结果的Map
           */
          public Map<String, String> getMapVote() {
                    return mapVote;
          }
          /**
           * 投票
           * @param user 投票人
           * @param voteItem 投票的选项
           */
          public void vote(String user, String voteItem){
                    Integer oldVoteCount = mapVoteCount.get(user);
                    if(oldVoteCount == null){
                           oldVoteCount = 0;
                    }
                    oldVoteCount++;
                    mapVoteCount.put(user, oldVoteCount);
                    if(oldVoteCount == 1){
                             state = new NormalVoteState();
                    }else if(oldVoteCount > 1 && oldVoteCount < 5){
                             state = new RepeatVoteState();
                    }else if(oldVoteCount >= 5 && oldVoteCount < 8){
                             state = new SpiteVoteState();
                    }else if(oldVoteCount >= 8){
                             state = new BlackVoteState();
                    }
                    state.vote(user, voteItem, this);
           }
}

public class Client {

          public static void main(String[] args) {
                    VoteManager manager = new VoteManager();
                    for(int i = 0; i < 8; i++){
                           manager.vote("JOE", "A");
                    }
          } 
}

#########################################################################################################

◆ 在状态处理类中进行状态的维护和转换

public interface VoteState {

          public void vote(String user, String voteItem, VoteManager manager);
}

public class NormalVoteState implements VoteState {

          @Override
          public void vote(String user, String voteItem, VoteManager manager) {
                    manager.getMapVote().put(user, voteItem);
                    System.out.println("投票成功！");
                    manager.getMapState().put(user, new RepeatVoteState());
         }
}

public class RepeatVoteState implements VoteState {

          @Override
          public void vote(String user, String voteItem, VoteManager manager) {
                    System.out.println("请不要重复投票。");
                    if(manager.getMapVoteCount().get(user) >= 4){
                             manager.getMapState().put(user, new SpiteVoteState());
                    }
         }
}
public class SpiteVoteState implements VoteState {

          @Override
          public void vote(String user, String voteItem, VoteManager manager) {
                    String s = manager.getMapVote().get(user);
                    if(s != null){
                             manager.getMapVote().remove(user);
                    }
                    System.out.println("你有恶意刷票行为，取消投票资格。");
                   if(manager.getMapVoteCount().get(user) >= 7){
                              manager.getMapState().put(user, new BlackVoteState());
                   }
         }
}

public class BlackVoteState implements VoteState {

          @Override
          public void vote(String user, String voteItem, VoteManager manager) {
                     System.out.println("你进入了黑名单。");
          }
}

public class VoteManager {
          /**
           * 记录当前每个用户对应的状态处理对象，每个用户当前的状态是不同的
           * Map<String, VoteState>对应Map<用户名，当前对应的状态处理对象>
           */
          private Map<String, VoteState> mapState = new HashMap<String, VoteState>();
          /**
           * 记录用户投票的结果，Map<String,String>对应Map<用户名，投票的选项>
           */
          private Map<String, String> mapVote = new HashMap<String, String>();
          /**
           * 记录用户投票次数，Map<String,Integer> 对应Map<用户名，投票的次数>
           */
          private Map<String, Integer> mapVoteCount = new HashMap<String, Integer>();
          /**
           * 获取记录用户投票结果的Map
           * @return 记录用户投票结果的Map
           */
          public Map<String, String> getMapVote() {
                    return mapVote;
          }
          /**
           * 获取记录当前每个用户对应的状态处理对象
           * @return
           */
          public Map<String, VoteState> getMapState() {
                    return mapState;
          }
          /**
           * 获取记录每个用户对应的投票次数的Map
           * @return
           */
          public Map<String, Integer> getMapVoteCount() {
                    return mapVoteCount;
          }
 
          public void vote(String user, String voteItem){
                    Integer oldVoteCount = mapVoteCount.get(user);
                    if(oldVoteCount == null){
                             oldVoteCount = 0;
                    }
                   oldVoteCount++;
                   mapVoteCount.put(user, oldVoteCount);
  
                   VoteState state = mapState.get(user);
                   if(state == null){
                           state = new NormalVoteState();
                   }
                   state.vote(user, voteItem, this);
          } 
}

public class Client {

          public static void main(String[] args) {
                    VoteManager manager = new VoteManager();
                    for(int i = 0; i < 8; i++){
                           manager.vote("JOE", "A");
                    }
          } 
}