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学通java的24堂课p447
发表在Java图书答疑
2016-02-07
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学通java的24堂课p447/15.08,怎么一运行,就出现java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:264)
at com.lw.DBHelper.getConnection(DBHelper.java:17)
at com.lw.DBHelper.openStatement(DBHelper.java:30)
at com.lw.DBHelper.query(DBHelper.java:49)
at com.lw.SQLDemo.main(SQLDemo.java:9)
Exception in thread "main" java.lang.NullPointerException
at com.lw.DBHelper.openStatement(DBHelper.java:30)
at com.lw.DBHelper.query(DBHelper.java:49)
at com.lw.SQLDemo.main(SQLDemo.java:9)
at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:264)
at com.lw.DBHelper.getConnection(DBHelper.java:17)
at com.lw.DBHelper.openStatement(DBHelper.java:30)
at com.lw.DBHelper.query(DBHelper.java:49)
at com.lw.SQLDemo.main(SQLDemo.java:9)
Exception in thread "main" java.lang.NullPointerException
at com.lw.DBHelper.openStatement(DBHelper.java:30)
at com.lw.DBHelper.query(DBHelper.java:49)
at com.lw.SQLDemo.main(SQLDemo.java:9)