MySQL JDBC连接停止工作

密码应为“root”。程序不会在catch块中显示消息，并停止工作。谁能告诉我发生了什么事

[更新] 对不起，我问了一个不好的问题。问题已经解决了，谢谢。这有助于正确检查连接是否存在

String url = "jdbc:mysql://localhost:3306/mysql";
String user = "root";
String pass = "root1";

try {
    Class.forName("com.mysql.jdbc.Driver");
    Connection connection = DriverManager.getConnection(url, user, pass);
    System.out.println("Connected to database");
} catch (Exception e) {         
    System.out.println(e);
    System.out.println("Could not connect to database");
}

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有三种不同的方式连接到SQL数据库，如下代码所示

if (conn1 != null) {
    System.out.println("Connected to the database test1");
}

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尝试将catch块中的stackTrace打印为

e.printStackTrace（）

，并将该错误粘贴到此处。它不会在控制台中显示任何内容，只需在此处停止即可。它没有进入catch块。试着注释这一行

Class.forName（“com.mysql.jdbc.Driver”）并重新运行。让我们看看…尝试使用Debugger这如何回答问题？检查连接是否存在有帮助。如果（conn1！=null）{System.out.println（“连接到数据库test1”）；}
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;

public class MySQLConnectExample {
    public static void main(String[] args) {

        // creates three different Connection objects
        Connection conn1 = null;
        Connection conn2 = null;
        Connection conn3 = null;

        try {
            // connect way #1
            String url1 = "jdbc:mysql://localhost:3306/test1";
            String user = "root";
            String password = "secret";

            conn1 = DriverManager.getConnection(url1, user, password);
            if (conn1 != null) {
                System.out.println("Connected to the database test1");
            }

            // connect way #2
            String url2 = "jdbc:mysql://localhost:3306/test2?user=root&password=secret";
            conn2 = DriverManager.getConnection(url2);
            if (conn2 != null) {
                System.out.println("Connected to the database test2");
            }

            // connect way #3
            String url3 = "jdbc:mysql://localhost:3306/test3";
            Properties info = new Properties();
            info.put("user", "root");
            info.put("password", "secret");

            conn3 = DriverManager.getConnection(url3, info);
            if (conn3 != null) {
                System.out.println("Connected to the database test3");
            }
        } catch (SQLException ex) {
            System.out.println("An error occurred. Maybe user/password is invalid");
            ex.printStackTrace();
        }
    }
}