public class MyDataSource {
</span><span style="color: rgba(0, 0, 255, 1)">private</span> <span style="color: rgba(0, 0, 255, 1)">static</span> LinkedList&lt;Connection&gt; pool = <span style="color: rgba(0, 0, 255, 1)">new</span> LinkedList&lt;&gt;<span style="color: rgba(0, 0, 0, 1)">();

</span><span style="color: rgba(0, 0, 255, 1)">private</span> <span style="color: rgba(0, 0, 255, 1)">static</span> <span style="color: rgba(0, 0, 255, 1)">final</span> <span style="color: rgba(0, 0, 255, 1)">int</span> INIT_CONNECTIONS = 10<span style="color: rgba(0, 0, 0, 1)">;

</span><span style="color: rgba(0, 0, 255, 1)">private</span> <span style="color: rgba(0, 0, 255, 1)">static</span> <span style="color: rgba(0, 0, 255, 1)">final</span> String DRIVER_NAME = "com.mysql.jdbc.Driver"<span style="color: rgba(0, 0, 0, 1)">;

</span><span style="color: rgba(0, 0, 255, 1)">private</span> <span style="color: rgba(0, 0, 255, 1)">static</span> <span style="color: rgba(0, 0, 255, 1)">final</span> String URL = ""<span style="color: rgba(0, 0, 0, 1)">;

</span><span style="color: rgba(0, 0, 255, 1)">private</span> <span style="color: rgba(0, 0, 255, 1)">static</span> <span style="color: rgba(0, 0, 255, 1)">final</span> String USER = ""<span style="color: rgba(0, 0, 0, 1)">;

</span><span style="color: rgba(0, 0, 255, 1)">private</span> <span style="color: rgba(0, 0, 255, 1)">static</span> <span style="color: rgba(0, 0, 255, 1)">final</span> String PASSWORD = ""<span style="color: rgba(0, 0, 0, 1)">;

</span><span style="color: rgba(0, 0, 255, 1)">static</span><span style="color: rgba(0, 0, 0, 1)"> {
    </span><span style="color: rgba(0, 0, 255, 1)">try</span><span style="color: rgba(0, 0, 0, 1)"> {
        Class.forName(DRIVER_NAME);
        </span><span style="color: rgba(0, 0, 255, 1)">for</span> (<span style="color: rgba(0, 0, 255, 1)">int</span> i = 0; i &lt; INIT_CONNECTIONS; i++<span style="color: rgba(0, 0, 0, 1)">) {
            Connection connection </span>=<span style="color: rgba(0, 0, 0, 1)"> DriverManager.getConnection(URL, USER, PASSWORD);
            pool.addLast(connection);
        }
    } </span><span style="color: rgba(0, 0, 255, 1)">catch</span><span style="color: rgba(0, 0, 0, 1)"> (Exception e) {
        e.printStackTrace();
    }
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span><span style="color: rgba(0, 0, 0, 1)"> Connection getConnection() {
    </span><span style="color: rgba(0, 0, 255, 1)">synchronized</span><span style="color: rgba(0, 0, 0, 1)"> (pool) {
        </span><span style="color: rgba(0, 0, 255, 1)">while</span> (pool.size() &lt;= 0<span style="color: rgba(0, 0, 0, 1)">) {
            </span><span style="color: rgba(0, 0, 255, 1)">try</span><span style="color: rgba(0, 0, 0, 1)"> {
                wait();
            } </span><span style="color: rgba(0, 0, 255, 1)">catch</span><span style="color: rgba(0, 0, 0, 1)"> (InterruptedException e) {
                e.printStackTrace();
            }
        }

        </span><span style="color: rgba(0, 0, 255, 1)">if</span> (!<span style="color: rgba(0, 0, 0, 1)">pool.isEmpty()) {
            </span><span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> pool.removeFirst();
        }
    }
    </span><span style="color: rgba(0, 0, 255, 1)">return</span> <span style="color: rgba(0, 0, 255, 1)">null</span><span style="color: rgba(0, 0, 0, 1)">;
}

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> releaseConnection(Connection connection) {
    </span><span style="color: rgba(0, 0, 255, 1)">if</span> (connection != <span style="color: rgba(0, 0, 255, 1)">null</span><span style="color: rgba(0, 0, 0, 1)">) {
        </span><span style="color: rgba(0, 0, 255, 1)">synchronized</span><span style="color: rgba(0, 0, 0, 1)"> (pool) {
            pool.addLast(connection);
            notifyAll();
        }
    }
}

}