java单例设计模式实例

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单例模式是一种常用的软件设计模式。在它的核心结构中只包含一个被称为单例的特殊类。通过单例模式可以保证系统中一个类只有一个实例，可以节约开销，提高系统性能。

单例模式的实现1.构造方法私有化2.内部提供公有的方法返回实例化的类

github下载地址https://github.com/gukunpja/signle.git

import java.sql.Connection;import java.sql.DriverManager;import java.sql.SQLException;import java.sql.Statement;/** * 单例模式数据库连接 *  * @author gxk * */public class JdbcSignle {private String url = "jdbc:mysql://localhost:3306/user";private String user = "root";private String pwd = "guxinkai";private static JdbcSignle Singleton;Statement  stmt = null;Connection conn = null;private JdbcSignle() {}public static JdbcSignle getInstance() {if (Singleton == null) {Singleton = new JdbcSignle();}return Singleton;}public void getConnection() throws Exception {Class.forName("com.mysql.jdbc.Driver");conn = DriverManager.getConnection(url, user, pwd);String sql = "insert into user values (1,'顾新凯')";stmt = conn.createStatement();int rs = stmt.executeUpdate(sql);System.out.println(rs);}public void closeConnection() throws Exception {if (stmt != null) {try {stmt.close();} catch (Exception e) {throw new RuntimeException(e);}}if (conn != null) {try {conn.close();} catch (Exception e) {throw new RuntimeException(e);}}}}

import org.junit.Test;public class JdbcSignleTest {@Testpublic void testJdbcSignle() throws Exception {JdbcSignle Singleton = JdbcSignle.getInstance();Singleton.getConnection();Singleton.closeConnection();}}

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