23种设计模式学习之享元模式

典型:各种连接池

    public class ConnectionPool {  
          
        private Vector<Connection> pool;  
          
        /*公有属性*/  
        private String url = "jdbc:mysql://localhost:3306/test";  
        private String username = "root";  
        private String password = "root";  
        private String driverClassName = "com.mysql.jdbc.Driver";  
      
        private int poolSize = 100;  
        private static ConnectionPool instance = null;  
        Connection conn = null;  
      
        /*构造方法，做一些初始化工作*/  
        private ConnectionPool() {  
            pool = new Vector<Connection>(poolSize);  
      
            for (int i = 0; i < poolSize; i++) {  
                try {  
                    Class.forName(driverClassName);  
                    conn = DriverManager.getConnection(url, username, password);  
                    pool.add(conn);  
                } catch (ClassNotFoundException e) {  
                    e.printStackTrace();  
                } catch (SQLException e) {  
                    e.printStackTrace();  
                }  
            }  
        }  
      
        /* 返回连接到连接池 */  
        public synchronized void release() {  
            pool.add(conn);  
        }  
      
        /* 返回连接池中的一个数据库连接 */  
        public synchronized Connection getConnection() {  
            if (pool.size() > 0) {  
                Connection conn = pool.get(0);  
                pool.remove(conn);  
                return conn;  
            } else {  
                return null;  
            }  
        }  
    }