示例代码:public class CustomClassLoader extends ClassLoader {private String classPath;public CustomClassLoader(String classPath) {super(null); this.classPath = classPath;}@Overrideprotected Class<?> findClass(String name) throws ClassNotFoundException {byte[] classData = loadClassData(name);if (classData == null) {throw new ClassNotFoundException();} else {return defineClass(name, classData, 0, classData.length);}}@Overridepublic Class<?> loadClass(String name) throws ClassNotFoundException {if (name.startsWith("java.")) {return super.loadClass(name); }try {return findClass(name); } catch (ClassNotFoundException e) {return super.loadClass(name); }}private byte[] loadClassData(String className) {String filePath = classPath + className.replace('.', '/') + ".class";try (InputStream inputStream = new FileInputStream(filePath);ByteArrayOutputStream byteStream = new ByteArrayOutputStream()) {int nextValue;while ((nextValue = inputStream.read()) != -1) {byteStream.write(nextValue);}return byteStream.toByteArray();} catch (IOException e) {e.printStackTrace();return null;}}public static void main(String[] args) {String classPath = "path_to_classes/";CustomClassLoader customClassLoader = new CustomClassLoader(classPath);try {Class<?> clazz = customClassLoader.loadClass("com.example.MyClass");Object instance = clazz.newInstance();System.out.println(instance.getClass().getName());} catch (ClassNotFoundException | InstantiationException | IllegalAccessException e) {e.printStackTrace();}}
}