public class DBPool { private static LinkedList<Connection> pool = new LinkedList <Connection>(); //限制了线程的最大连接数，一般还有最小连接，最大连接数定义为20 public DBPool ( int initialSize) { if (initialSize > 0 ) { for ( int i = 0 ; i < initialSize; i++) {                  pool.addLast(SqlConnectImpl.fetchConnection()); //释放连接，用完后放回连接池，通知其他等待连接的应用 public void releaseConnection (Connection connection) { if (connection != null ) { //TODO这个池子不空了，通知其他等待连接的线程 synchronized (pool){                  pool.addLast(connection); //通知其他等待连接的线程 pool.notifyAll(); // 在mills(超时时长)内无法获取到连接，将会返回null，真正的还要抛出异常去 //数据库连接池的大体实现思路 //获取连接 public Connection fetchConnection ( long mills) throws InterruptedException { //TODO同一时刻只能有一个线程操作数据库 synchronized (pool){ //永不超时 if (mills< 0 ){ //去拿连接 while (pool.isEmpty()){                      wait(); //从尾巴放，从头拿 return pool.removeFirst();             } else { //获取超时的时刻，什么时候超时 long furture = System.currentTimeMillis()+mills; //需要等待多久 long remaining = mills; while (pool.isEmpty()&&remaining> 0 ){ //这个时候需要用pool调用wait方法：注意wait的调用 pool.wait(remaining); //等那么久 //每被唤醒后，需要重新计算等待时间(因为有可能是抢不到的) remaining = furture-System.currentTimeMillis(); //跳出这个while循环，那么就是两种情况(要么成功拿到CPU--->去连接池里面拿连接， // 要么等待时间结束了--->返回一个空的连接，返回调用者，告诉他，他在没有抢到并且时间结束了) Connection connection = null ; //当抢到了CPU，这个时候就要去连接池里面拿东西了同时排除了那种因为超时进来的； if (!pool.isEmpty()){                      connection = pool.removeFirst(); return connection;

DBTest.java

 package cn.enjoyedu.ch1.pool;
 import java.sql.Connection;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.atomic.AtomicInteger;
  *类说明：
 public class DBPoolTest {
     static DBPool pool  = new DBPool(20);
     // 控制器:控制main线程将会等待所有Woker结束后才能继续执行，控制所有线程一起执行工作
     static CountDownLatch end;
     //定义了50个线程，每一个线程尝试去数据库连接池中拿20次
     public static void main(String[] args) throws Exception {
         // 线程数量
         int threadCount = 50;
         end = new CountDownLatch(threadCount);
         int count = 20;//每个线程的操作次数
         //原子变量，保证线程安全性
         AtomicInteger got = new AtomicInteger();//计数器：统计可以拿到连接的线程
         AtomicInteger notGot = new AtomicInteger();//计数器：统计没有拿到连接的线程
         for (int i = 0; i < threadCount; i++) {
             Thread thread = new Thread(new Worker(count, got, notGot), 
                     "worker_"+i);
             thread.start();
         end.await();// main线程在此处等待
         System.out.println("总共尝试了: " + (threadCount * count));
         System.out.println("拿到连接的次数：  " + got);
         System.out.println("没能连接的次数： " + notGot);
     static class Worker implements Runnable {
         int           count;
         AtomicInteger got;
         AtomicInteger notGot;
         public Worker(int count, AtomicInteger got,
                                AtomicInteger notGot) {
             this.count = count;
             this.got = got;
             this.notGot = notGot;
         public void run() {
             while (count > 0) {
                 try {
                     // 从线程池中获取连接，如果1000ms内无法获取到，将会返回null
                     // 分别统计连接获取的数量got和未获取到的数量notGot
                     Connection connection = pool.fetchConnection(1000);
                     if (connection != null) {
                         try {
                             //拿到连接后，进行数据库操作
                             connection.createStatement();
                             connection.commit();
                         } finally {
                             //连接耍完了，那么就将这个连接重新放回数据库连接池
                             pool.releaseConnection(connection);
                             //统计这种成功的次数
                             got.incrementAndGet();
                     } else {
                         //当这个拿到的连接时空的，就统计这些失败后的问题
                         notGot.incrementAndGet();
                         System.out.println(Thread.currentThread().getName()
                                 +"等待超时!");
                 } catch (Exception ex) {
                 } finally {
                     count--;
             end.countDown();
SqlConnectImpl.java 重写了大量的方法
  package cn.enjoyedu.ch1.pool;
     import cn.enjoyedu.tools.SleepTools;
     import java.sql.*;
     import java.util.Map;
     import java.util.Properties;
     import java.util.concurrent.Executor;
      *类说明：
     public class SqlConnectImpl implements Connection{
     /*拿一个数据库连接*/
 public static final Connection fetchConnection(){
     return new SqlConnectImpl();
 @Override
 public boolean isWrapperFor(Class<?> arg0) throws SQLException {
         // TODO Auto-generated method stub
         return false;
 @Override
 public <T> T unwrap(Class<T> arg0) throws SQLException {
         // TODO Auto-generated method stub
         return null;
 @Override
 public void abort(Executor arg0) throws SQLException {
         // TODO Auto-generated method stub
 @Override
 public void clearWarnings() throws SQLException {
         // TODO Auto-generated method stub
 @Override
 public void close() throws SQLException {
         // TODO Auto-generated method stub
 @Override
 public void commit() throws SQLException {
         SleepTools.ms(70);
 @Override
 public Array createArrayOf(String arg0, Object[] arg1) throws SQLException {
         // TODO Auto-generated method stub
         return null;
 @Override
 public Blob createBlob() throws SQLException {
         // TODO Auto-generated method stub
         return null;
 @Override
 public Clob createClob() throws SQLException {
         // TODO Auto-generated method stub
         return null;
 @Override
 public NClob createNClob() throws SQLException {
         // TODO Auto-generated method stub
         return null;
 @Override
 public SQLXML createSQLXML() throws SQLException {
         // TODO Auto-generated method stub
         return null;
 @Override
 public Statement createStatement() throws SQLException {
         SleepTools.ms(1);
         return null;
 @Override
 public Statement createStatement(int arg0, int arg1) throws SQLException {
         // TODO Auto-generated method stub
         return null;
 @Override
 public Statement createStatement(int arg0, int arg1, int arg2) throws SQLException {
         // TODO Auto-generated method stub
         return null;
 @Override
 public Struct createStruct(String arg0, Object[] arg1) throws SQLException {
         // TODO Auto-generated method stub
         return null;
 @Override
 public boolean getAutoCommit() throws SQLException {
         // TODO Auto-generated method stub
         return false;
 @Override
 public String getCatalog() throws SQLException {
         // TODO Auto-generated method stub
         return null;
 @Override
 public Properties getClientInfo() throws SQLException {
         // TODO Auto-generated method stub
         return null;
 @Override
 public String getClientInfo(String arg0) throws SQLException {
         // TODO Auto-generated method stub
         return null;
 @Override
 public int getHoldability() throws SQLException {
         // TODO Auto-generated method stub
         return 0;
 @Override
 public DatabaseMetaData getMetaData() throws SQLException {
         // TODO Auto-generated method stub
         return null;
 @Override
 public int getNetworkTimeout() throws SQLException {
         // TODO Auto-generated method stub
         return 0;
 @Override
 public String getSchema() throws SQLException {
         // TODO Auto-generated method stub
         return null;
 @Override
 public int getTransactionIsolation() throws SQLException {
         // TODO Auto-generated method stub
         return 0;
 @Override
 public Map<String, Class<?>> getTypeMap() throws SQLException {
         // TODO Auto-generated method stub
         return null;
 @Override
 public SQLWarning getWarnings() throws SQLException {
         // TODO Auto-generated method stub
         return null;
 @Override
 public boolean isClosed() throws SQLException {
         // TODO Auto-generated method stub
         return false;
 @Override
 public boolean isReadOnly() throws SQLException {
         // TODO Auto-generated method stub
         return false;
 @Override
 public boolean isValid(int arg0) throws SQLException {
         // TODO Auto-generated method stub
         return false;
 @Override
 public String nativeSQL(String arg0) throws SQLException {
         // TODO Auto-generated method stub
         return null;
 @Override
 public CallableStatement prepareCall(String arg0) throws SQLException {
         // TODO Auto-generated method stub
         return null;
 @Override
 public CallableStatement prepareCall(String arg0, int arg1, int arg2) throws SQLException {
         // TODO Auto-generated method stub
         return null;
 @Override
 public CallableStatement prepareCall(String arg0, int arg1, int arg2, int arg3) throws SQLException {
         // TODO Auto-generated method stub
         return null;
 @Override
 public PreparedStatement prepareStatement(String arg0) throws SQLException {
         // TODO Auto-generated method stub
         return null;
 @Override
 public PreparedStatement prepareStatement(String arg0, int arg1) throws SQLException {
         // TODO Auto-generated method stub
         return null;
 @Override
 public PreparedStatement prepareStatement(String arg0, int[] arg1) throws SQLException {
         // TODO Auto-generated method stub
         return null;
 @Override
 public PreparedStatement prepareStatement(String arg0, String[] arg1) throws SQLException {
         // TODO Auto-generated method stub
         return null;
 @Override
 public PreparedStatement prepareStatement(String arg0, int arg1, int arg2) throws SQLException {
         // TODO Auto-generated method stub
         return null;
 @Override
 public PreparedStatement prepareStatement(String arg0, int arg1, int arg2, int arg3) throws SQLException {
         // TODO Auto-generated method stub
         return null;
 @Override
 public void releaseSavepoint(Savepoint arg0) throws SQLException {
         // TODO Auto-generated method stub
 @Override
 public void rollback() throws SQLException {
         // TODO Auto-generated method stub
 @Override
 public void rollback(Savepoint arg0) throws SQLException {
         // TODO Auto-generated method stub
 @Override
 public void setAutoCommit(boolean arg0) throws SQLException {
         // TODO Auto-generated method stub
 @Override
 public void setCatalog(String arg0) throws SQLException {
         // TODO Auto-generated method stub
 @Override
 public void setClientInfo(Properties arg0) throws SQLClientInfoException {
         // TODO Auto-generated method stub
 @Override
 public void setClientInfo(String arg0, String arg1) throws SQLClientInfoException {
         // TODO Auto-generated method stub
 @Override
 public void setHoldability(int arg0) throws SQLException {
         // TODO Auto-generated method stub
 @Override
 public void setNetworkTimeout(Executor arg0, int arg1) throws SQLException {
         // TODO Auto-generated method stub
 @Override
 public void setReadOnly(boolean arg0) throws SQLException {
         // TODO Auto-generated method stub
 @Override
 public Savepoint setSavepoint() throws SQLException {
         // TODO Auto-generated method stub
         return null;
 @Override
 public Savepoint setSavepoint(String arg0) throws SQLException {
         // TODO Auto-generated method stub
         return null;
 @Override
 public void setSchema(String arg0) throws SQLException {
         // TODO Auto-generated method stub
 @Override
 public void setTransactionIsolation(int arg0) throws SQLException {
         // TODO Auto-generated method stub
 @Override
 public void setTypeMap(Map<String, Class<?>> arg0) throws SQLException {
         // TODO Auto-generated method stub
     public static void main(String[] args) {
         SleepLock sleepTest = new SleepLock();
         Thread threadA = sleepTest.new ThreadSleep();
         threadA.setName("ThreadSleep");
         Thread threadB = sleepTest.new ThreadNotSleep();
         threadB.setName("ThreadNotSleep");
         threadA.start();
         try {
             Thread.sleep(1000);
             System.out.println(" Main slept!");
         } catch (InterruptedException e) {
             e.printStackTrace();
         threadB.start();
     private class ThreadSleep extends Thread{
         @Override
         public void run() {
             String threadName = Thread.currentThread().getName();
             System.out.println(threadName+" will take the lock");
             try {
                 synchronized(lock) {
                     System.out.println(threadName+" taking the lock");
                     Thread.sleep(5000);
                     System.out.println("Finish the work: "+threadName);
             } catch (InterruptedException e) {
                 //e.printStackTrace();
     private class ThreadNotSleep extends Thread{
         @Override
         public void run() {
             String threadName = Thread.currentThread().getName();
             System.out.println(threadName+" will take the lock time="+System.currentTimeMillis());
             synchronized(lock) {
                 System.out.println(threadName+" taking the lock time="+System.currentTimeMillis());
                 System.out.println("Finish the work: "+threadName);