public class ClassLoaderTest {

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

        ClassLoader myClassLoader = new ClassLoader() {
            /**
             * Loads the class with the specified <a href="#name">binary name</a>.
             * This method searches for classes in the same manner as the {@link
             * #loadClass(String, boolean)} method.  It is invoked by the Java virtual
             * machine to resolve class references.  Invoking this method is equivalent
             * to invoking {@link #loadClass(String, boolean) <tt>loadClass(name,
             * false)</tt>}.
             *
             * @param name The <a href="#name">binary name</a> of the class
             * @return The resulting <tt>Class</tt> object
             * @throws ClassNotFoundException If the class was not found
             */
            @Override
            public Class<?> loadClass(String name) throws ClassNotFoundException {
                try{
                    String fileName = name.substring(name.lastIndexOf(".")+1)+".class";

                    InputStream inputStream = getClass().getResourceAsStream(fileName);
                    if(null == inputStream){
                        return super.loadClass(name);
                    }
                    byte[] b = new byte[inputStream.available()];
                    inputStream.read(b);
                    return defineClass(name,b,0,b.length);
                }catch (IOException e){
                    throw new ClassNotFoundException(name);
                }

            }
        };

        Object obj = myClassLoader.loadClass("com.eurekaclient2.client2.shejimoshi.JVM.ClassLoaderTest").newInstance();

        System.out.println("來源："+obj.getClass());

        System.out.println(obj instanceof com.eurekaclient2.client2.shejimoshi.JVM.ClassLoaderTest);
    }

}

來源：class com.eurekaclient2.client2.shejimoshi.JVM.ClassLoaderTest
false

/**
     * Loads the class with the specified <a href="#name">binary name</a>.  The
     * default implementation of this method searches for classes in the
     * following order:
     *
     * <ol>
     *
     *   <li><p> Invoke {@link #findLoadedClass(String)} to check if the class
     *   has already been loaded.  </p></li>
     *
     *   <li><p> Invoke the {@link #loadClass(String) <tt>loadClass</tt>} method
     *   on the parent class loader.  If the parent is <tt>null</tt> the class
     *   loader built-in to the virtual machine is used, instead.  </p></li>
     *
     *   <li><p> Invoke the {@link #findClass(String)} method to find the
     *   class.  </p></li>
     *
     * </ol>
     *
     * <p> If the class was found using the above steps, and the
     * <tt>resolve</tt> flag is true, this method will then invoke the {@link
     * #resolveClass(Class)} method on the resulting <tt>Class</tt> object.
     *
     * <p> Subclasses of <tt>ClassLoader</tt> are encouraged to override {@link
     * #findClass(String)}, rather than this method.  </p>
     *
     * <p> Unless overridden, this method synchronizes on the result of
     * {@link #getClassLoadingLock <tt>getClassLoadingLock</tt>} method
     * during the entire class loading process.
     *
     * @param  name
     *         The <a href="#name">binary name</a> of the class
     *
     * @param  resolve
     *         If <tt>true</tt> then resolve the class
     *
     * @return  The resulting <tt>Class</tt> object
     *
     * @throws  ClassNotFoundException
     *          If the class could not be found
     */
    protected Class<?> loadClass(String name, boolean resolve)
        throws ClassNotFoundException
    {
        synchronized (getClassLoadingLock(name)) {
            // First, check if the class has already been loaded
            Class<?> c = findLoadedClass(name);
            if (c == null) {
                long t0 = System.nanoTime();
                try {
                    if (parent != null) {
                        c = parent.loadClass(name, false);
                    } else {
                        c = findBootstrapClassOrNull(name);
                    }
                } catch (ClassNotFoundException e) {
                    // ClassNotFoundException thrown if class not found
                    // from the non-null parent class loader
                }

                if (c == null) {
                    // If still not found, then invoke findClass in order
                    // to find the class.
                    long t1 = System.nanoTime();
                    c = findClass(name);

                    // this is the defining class loader; record the stats
                    sun.misc.PerfCounter.getParentDelegationTime().addTime(t1 - t0);
                    sun.misc.PerfCounter.getFindClassTime().addElapsedTimeFrom(t1);
                    sun.misc.PerfCounter.getFindClasses().increment();
                }
            }
            if (resolve) {
                resolveClass(c);
            }
            return c;
        }
    }