public class URLtest extends ClassLoader{ public Class findClass(String name,byte[] b) { return defineClass(name, b, 0, b.length); } public static void main(String arg[]){ try { //按照类文件路径加载 URL url=new URL("file:/E:\\yunta\\Testclass\\src\\TestClass.class"); URLClassLoader classloader=new URLClassLoader(new URL[]{url}); Class> c = classloader.loadClass("TestClass"); Object o = c.newInstance(); Method method = c.getMethod("say"); method.invoke(o, null); //从io流中加载 InputStream in = new FileInputStream(new File("E:\\yunta\\Testclass\\src\\TestClass.class")); ByteArrayOutputStream butter = new ByteArrayOutputStream(); int i=0; int j=0; while(((i=in.read()))!=-1){ butter.write(i); } byte[] d = butter.toByteArray(); Class c1 = URLtest.class.newInstance().findClass("TestClass", d); Object o1 = c1.newInstance(); Method method1 = c1.getMethod("say"); try { method1.invoke(o1, null); ： ： ： ： ：