动态生成编译运行java类

本代码并非原创,是在我以前的学习笔记里面翻阅出来的,是csdn里面一位叫路人甲的朋友在论坛里面的回复,也许在这里发出来会帮助到很多朋友.其实十分简单就不加注释了,一共就3步,生成java文件,编译java文件,运行java类,

 

package  com.syj;

import  java.io.File;
import  java.io.FileWriter;
import  java.lang.reflect.Method;

public   class  CreateClass {
     private   static  String CLASS_NAME  =   " CreateClassTest " ;
     private   static  String CLASS_FILE  =  CLASS_NAME  +   " .java " ;

     public   static   void  main(String args[]) {
        CreateClass mtc  =   new  CreateClass();
        mtc.createClass();
        System.out.println( " javac  "   +  CLASS_FILE);
        mtc.compileClass();
        System.out.println( " java  "   +  CLASS_NAME);
        mtc.runClass();
    }

     public   void  createClass() {
         try  {
             new  File(CLASS_FILE).delete();
            FileWriter aWriter  =   new  FileWriter(CLASS_FILE,  true );
            aWriter.write( " public   class    "   +  CLASS_NAME  +   " { " );
            aWriter.write( " public   void   println()   { " );
            aWriter.write( " System.out.println("= "   +  CLASS_NAME  +   " ="); " );
            aWriter.write( " }} " );
            aWriter.flush();
            aWriter.close();
        }  catch  (Exception e) {
            e.printStackTrace();
        }
    }

     public   void  compileClass() {
        String filePath  =   new  File(CreateClass. class .getClassLoader()
                .getResource( "" ).getFile()).getAbsolutePath();
        String[] source  =  {  " -d " , filePath,  new  String(CLASS_FILE) };
        System.out.println( " javac out: "
                 +  com.sun.tools.javac.Main.compile(source));
    }

     public   void  runClass() {
         try  {
            Class params[]  =  {};
            Object paramsObj[]  =  {};
            Class testClass  =  Class.forName(CLASS_NAME);
            Object iClass  =  testClass.newInstance();
            Method thisMethod  =  testClass.getDeclaredMethod( " println " , params);
            thisMethod.invoke(iClass, paramsObj);
        }  catch  (Exception e) {
            e.printStackTrace();
        }
    }
}

需要引入%JAVA_HOME%/lib/tools.jar;这也是我遇到的tools.jar的唯一一个用途呵呵.