DBConnectionPool

package DBConnectionPool;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.TimeUnit;

public class DBConnectionPool {
	
	private final BlockingQueue<Connection> pool;
	private final String dbUrl;
	private final String dbUser;
	private final String dbPassword;
	private int poolSize;

	public DBConnectionPool(String dbUrl,String dbUser,String dbPassword,int poolSize) throws SQLException {
		this.dbUrl=dbUrl;
		this.dbPassword=dbPassword;
		this.dbUser=dbUser;
		this.poolSize=poolSize;
		this.pool = new ArrayBlockingQueue<>(poolSize);
		
		for(int i=0;i<poolSize;i++) {
			pool.add(createNewConnection());
		}
		
	}
	
	private Connection createNewConnection() throws SQLException{
		return DriverManager.getConnection(dbUrl,dbUser,dbPassword);
	}
	
	public Connection borrowConnection(long timeout,TimeUnit unit) throws InterruptedException, SQLException {
		Connection connection=pool.poll(timeout,unit);
		
		if(connection==null) {
			throw new SQLException("Timed out while waiting for a connection");
		}
		System.out.println("Connection established");
		return connection;
	}
	
	public void retrunConnection(Connection connection) {
		if(connection!=null) {
			System.out.println("Connection returned");
			pool.offer(connection);
		}
	}
	
	public synchronized void shutdown() throws SQLException {
		for(Connection connection:pool) {
			if(connection!=null) {
				connection.close();
			}
		}
		pool.clear();
	}
	
	public static class task implements Runnable{
		
		private final DBConnectionPool pool;
		
		public task(DBConnectionPool pool) {
			this.pool=pool;	
		}
		
		@Override
		public void run() {
		Connection connection = null;
		try {	
			connection = pool.borrowConnection(5, TimeUnit.SECONDS);
			Thread.sleep(2000);
			
		} catch (InterruptedException | SQLException e1) {
		
			System.out.println(Thread.currentThread().getName()+" Failed to get DB Connection");
		}finally {
			if(connection!=null) {
				pool.retrunConnection(connection);
			}
		}
			
		}
		
	}
	
	public static void main(String[] args) throws SQLException, InterruptedException {
		
		DBConnectionPool pool=new DBConnectionPool("jdbc:mysql://localhost:3306/mydb","user","password",5);
		
		for(int i=0;i<5;i++) {
			new Thread(new task(pool)).start();
		}
		Thread.sleep(10000);
		pool.shutdown();
		
	}

}