请老师帮忙看一下，报下面的错误

java.lang.ClassNotFoundException: com.mysql.cj.jdbc.Driver

at java.net.URLClassLoader.findClass(Unknown Source)

at java.lang.ClassLoader.loadClass(Unknown Source)

at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)

at java.lang.ClassLoader.loadClass(Unknown Source)

at java.lang.Class.forName0(Native Method)

at java.lang.Class.forName(Unknown Source)

at com.imooc.jdbc.JDBCDemo1.demo1(JDBCDemo1.java:20)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)

at java.lang.reflect.Method.invoke(Unknown Source)

at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:45)

at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)

at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:42)

at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)

at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:263)

at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:68)

at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:47)

at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)

at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)

at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)

at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)

at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)

at org.junit.runners.ParentRunner.run(ParentRunner.java:300)

at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)

at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)

at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:538)

at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:760)

at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:460)

at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:206)

package com.imooc.jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import org.junit.Test;

/**
 * 
 * JDBC的入门程序
 */
public class JDBCDemo1 {
	@Test
	public void demo1() {
		try {
			// 1.加载驱动
			Class.forName("com.mysql.cj.jdbc.Driver");
			// 2.获得连接
			Connection conn = DriverManager.getConnection(
					"jdbc:mysql://localhost:3306/JDBC_test"
							+ "?useSSL=false&serverTimezone=Hongkong&useUnicode=true&characterEncoding=utf-8",
					"root", "115224");
			//3.创建执行SQL语句的对象，并且执行SQL
			//3.1创建执行sql的对象
			String sql = "select * from user";
			Statement stmt = conn.createStatement();
			//3.2执行sql
			ResultSet resultSet = stmt.executeQuery(sql);
			while(resultSet.next()) {
				int uid = resultSet.getInt("uid");
				String username = resultSet.getString("username");
				String password = resultSet.getString("password");
				String name = resultSet.getString("name");
				System.out.println(uid+" "+username+" "+password+" "+name);
			}
			//4.释放资源
			resultSet.close();
			stmt.close();
			conn.close();
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

}