运行一个非常简单的json小程序，运行就出现一堆红字异常、求解

public static void main(String[] args) {        // TODO Auto-generated method stub        prepareData();                for(Contact con:list){            JSONObject obj=new JSONObject();            try{            obj.put("name", con.getContact());            obj.put("num", con.getPhoneNum());            System.out.print(obj.getString("name"));            System.out.print(obj.getString("num"));            }catch(Exception  e){                            }

Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/lang/exception/NestableRuntimeException    at java.lang.ClassLoader.defineClass1(Native Method)    at java.lang.ClassLoader.defineClass(ClassLoader.java:621)    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)    at java.net.URLClassLoader.defineClass(URLClassLoader.java:260)    at java.net.URLClassLoader.access$000(URLClassLoader.java:56)    at java.net.URLClassLoader$1.run(URLClassLoader.java:195)    at java.security.AccessController.doPrivileged(Native Method)    at java.net.URLClassLoader.findClass(URLClassLoader.java:188)    at java.lang.ClassLoader.loadClass(ClassLoader.java:307)    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)    at java.lang.ClassLoader.loadClass(ClassLoader.java:252)    at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)    at JsonDemo.main(JsonDemo.java:20)Caused by: java.lang.ClassNotFoundException: org.apache.commons.lang.exception.NestableRuntimeException    at java.net.URLClassLoader$1.run(URLClassLoader.java:200)    at java.security.AccessController.doPrivileged(Native Method)    at java.net.URLClassLoader.findClass(URLClassLoader.java:188)    at java.lang.ClassLoader.loadClass(ClassLoader.java:307)    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)    at java.lang.ClassLoader.loadClass(ClassLoader.java:252)    at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)    ... 13 more