2、通过JavaCompiler动态编译。

import java.io.*;
import java.lang.reflect.Method;
import java.net.*;
import javax.tools.*;
/*
   测试Java动态编译
 */
public class 动态编译DynamicCompiler {

    public static void main(String[] args) throws Exception {

        //通过IO流操作，将字符串存储成一个临时文件(Hi.java)，然后调用动态编译方法！
        String str = "public class Hi {public static void main(String[] args){System.out.println(\"Hello\");}}";

        BufferedWriter bw = new BufferedWriter(
                new OutputStreamWriter(
                        new BufferedOutputStream(
                                new FileOutputStream("Hi.java"))));
        bw.write(str);
        bw.flush();
        bw.close();
        JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
        int result = compiler.run(null, null, null, "Hi.java");
        System.out.println(result==0?"编译成功":"编译失败");

        //通过Runtime调用执行类
	    Runtime run = Runtime.getRuntime();
        Process process = run.exec("java -cp  C:/Users/kvnoe/Desktop/Jcase    Hi");

        InputStream in = process.getInputStream();
        BufferedReader reader = new BufferedReader(new InputStreamReader(in));
		String info = "";
		while((info=reader.readLine())!=null){
			System.out.println(info);
		}
        
		//通过反射调用执行类
        try {
            URL[] urls = new URL[] {new URL("file:/"+"C:/Users/kvnoe/Desktop/Jcase/")};
            URLClassLoader loader = new URLClassLoader(urls);
            Class c = loader.loadClass("Hi");
            //调用加载类的main方法
            Method m = c.getMethod("main",String[].class);
            m.invoke(null, (Object)new String[]{});
            //由于可变参数是JDK5.0之后才有。
            //m.invoke(null, (Object)new String[]{});会编译成:m.invoke(null,"aa","bb"),就发生了参数个数不匹配的问题。
            //因此，必须要加上(Object)转型，避免这个问题。
            //public static void main(String[] args)

        } catch (Exception e) {
            e.printStackTrace();
        }

    }
}