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一直对多线程有恐惧，在实现共享锁和排它锁之后，感觉好了很多。

共享锁    就是查询的时候，如果没有修改，可以支持多线程查询；

排它锁    就是修改的时候，锁定共享锁，停止查询，同时，锁定排它锁，只允许一个线程进行修改，修改完成后，再解开共享锁；

心路历程： 一开始的想法是，绝对不调用 sleep ，要用到sleep 的地方我觉得都可以用  notify() 和 wait() 替换，sleep(T) 我觉得T  的大小压根是无法算出来的，如果非要用sleep 我觉得T 的时间应该是一个动态的值，这个值是通过函数的执行时间的一个平均值(每N次执行算一个 平均值出来) 但个人觉得还是不如notify() 和wait(); 我为了简单，操作的是一颗字典树代替B树；如何实现读支持多线程，写单线程呢！ 当各种查询和修改的操作以多线程的方式提交给线程池的时候，程序会从阻塞队列里面不断的取任务，当前面取到的任务是 查询的时候，不要管他，没有修改表结构，直接丢给一个线程，当取到的下任务是一个修改或者更新的任务时，首先必须等待前面的查询全部查询完，然后再停掉阻塞队列不断的添加任务， 要让我修改完成之后，再唤醒阻塞队列添加任务；由于我不知道如何停掉线程池的阻塞队列添加任务，所以干脆自己模拟线程池这个过程；(理论上这个方法是可行的) 主要的卡是在notify() 和 wait()的理解上面，这两个方法执行时都必须在 锁里面； 所以在查询的代码里面，你不能wait() 那样会变成单线程；

1 insert; 2 remove;  3 query; -1 stopRun

1 packagecom.trafree;2

3 importjava.io.File;4 importjava.io.IOException;5 import java.util.*;6 importjava.util.concurrent.atomic.AtomicInteger;7

8 /**

9 * Created by on_the_way on 2014/12/31.10 */

11 public classAboutThread {12

13 public static booleaninsert(String str) {14 int len =str.length();15 Trie p =root;16 for (int i = 0; i < len; i++) {17 int num = str.charAt(i) - ‘a‘;18 if (p.next[num] == null) {19 p.next[num] = newTrie();20 }21 p =p.next[num];22 }23 if (p.end) return false;24 return p.end = true;25 }26

27 public static booleanremove(String str) {28 int len =str.length();29 Trie p =root;30 for (int i = 0; i < len; i++) {31 int num = str.charAt(i) - ‘a‘;32 if (p.next[num] == null) {33 return false;34 }35 p =p.next[num];36 }37 if (!p.end) {38 return false;39 }40 p.end = false;41 return true;42 }43

44 public static booleanquery(String str) {45 int len =str.length();46 Trie p =root;47 for (int i = 0; i < len; i++) {48 int num = str.charAt(i) - ‘a‘;49 if (p.next[num] == null) {50 return false;51 }52 p =p.next[num];53 }54 returnp.end;55 }56

57 public static Trie root = newTrie();58

59 public static classTrie {60 public Trie next[] = new Trie[26];61 public booleanend;62

63 publicTrie() {64 for (int i = 0; i < 26; i++) {65 this.next[i] = null;66 }67 this.end = false;68 }69 }70

71 public static class Consumer implementsRunnable {72 public voidrun() {73 try{74 MyThread.process();75 } catch(Exception e) {76 e.printStackTrace();77 }78 }79 }80

81 public static class MyThread implementsRunnable {82

83 public intsequence;84 public intaction;85 publicString str;86 public booleanres;87

88 public static Object lock1 = newObject();89 public static Object lock2 = newObject();90 public static Object lock3 = newObject();91

92 public static boolean needNotify1 = false;93 public static boolean needNotify2 = false;94 public static boolean needNotify3 = false;95 public static boolean runModify = false;96

97 public static AtomicInteger queryNum = new AtomicInteger(0);98 public static Queue pool = new LinkedList();99

100 public MyThread(int sequence, intaction, String str) {101 this.sequence =sequence;102 this.action =action;103 this.str =str;104 this.res = false;105 }106

107 public static void process() throwsInterruptedException {108

109 boolean needBreak = false;110 while (true) {111 if( pool.size() == 0 &&needBreak ){112 break;113 }114 synchronized(lock1) {115 if (pool.size() == 0) {116 needNotify1 = true;117 lock1.wait();118 }119 }120 synchronized(lock3) {121 if(runModify) {122 needNotify3 = true;123 lock3.wait();124 }125 }126 MyThread myThread =pool.poll();127

128 if (myThread.action == -1){129 needBreak = true;continue;130 }131 if (myThread.action == 1 || myThread.action == 2) {132 synchronized(lock2) {133 if (queryNum.get() != 0) {134 needNotify2 = true;135 runModify = true;136 lock2.wait();137 newThread(myThread).start();138 } else{139 runModify = true;140 newThread(myThread).start();141 }142 }143 } else{144 queryNum.incrementAndGet();145 newThread(myThread).start();146 }147 }148 }149

150 public voidrun() {151 if (this.action == 1) {152 this.res = insert(this.str);153 synchronized(lock3) {154 needNotify1 = false;155 runModify = false;156 if( needNotify3 )lock3.notify();157 }158 System.out.println(sequence+" "+action+" "+str+" "+res);159 } else if (this.action == 2) {160 this.res = remove(this.str);161 synchronized(lock3) {162 needNotify1 = false;163 runModify = false;164 if( needNotify3 )lock3.notify();165 }166 System.out.println(sequence+" "+action+" " + str+" "+res);167 } else{168 this.res =query(str);169 System.out.println(sequence+" "+action+" "+str+" "+res);170 synchronized(lock2) {171 if (queryNum.decrementAndGet() == 0) {172 if(needNotify2)lock2.notify();173 }174 }175 }176 }177

178 }179

180 public static void main(String arg[]) throwsIOException {181

182 File file = new File("F:" + File.separator + "in.txt");183 Scanner cin = newScanner(file);184 int N =cin.nextInt();185 int M =cin.nextInt();186

187 for (int i = 0; i < N; i++) {188 insert(cin.next());189 }190

191 new Thread(newConsumer()).start();192 for (int i = 0; i < M; i++) {193 MyThread myThread = newMyThread(i, cin.nextInt(), cin.next());194 synchronized(MyThread.lock1) {195 MyThread.pool.add(myThread);196 if(MyThread.needNotify1) {197 MyThread.needNotify1 = false;198 MyThread.lock1.notify();199 }200 }201 }202 }203 }

View Code

40 45

what

make

you

so

beautiful

have

think

cell

green

red

java

hand

forum

discuss

online

contests

teaching

exercise

contest

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icpc

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achive

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judge

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new

fortunately

old

behind

locked

the

feature

find

by

alphabet

more

3 what

3 more

3 old

3 find

3 exams

3 achive

3 icpc

3 recent

3 ranklist

2 ranklist

3 ranklist

1 ranklist

3 ranklist

3 find

3 alphabet

2 find

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3 find

2 alphabet

1 alphabet

3 alphabet

3 find

1 find

3 find

3 what

3 more

3 old

3 find

3 exams

3 achive

3 icpc

3 recent

3 ranklist

3 ranklist

3 what

3 more

3 old

3 find

3 exams

3 achive

3 icpc

3 recent

3 ranklist

3 ranklist

-1 end

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