I'm playing a little bit with ClassLoader. I write my own class loader and use it to load HelloWorld class. While loading HelloWorld class, the class loader can't find java.lang.object so it gives the exception as following:

Exception in thread "main" java.lang.NoClassDefFoundError: java/lang/Object
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClassCond(ClassLoader. java:632)
at java.lang.ClassLoader.defineClass(ClassLoader.java :616)
at CustomClassLoader.findClass(CustomClassLoader.java :28)
at CustomClassLoader.loadClass(CustomClassLoader.java :15)
at CustomClassLoaderTest.main(CustomClassLoaderTest.j ava:5)
I've checked the file rt.jar and it includes java/lang/Object.class already. Do you know how to fix this problem? Thank you so much.

Here is my class loader:

Java Code:
import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.Enumeration;
import java.util.Hashtable;

public class CustomClassLoader extends ClassLoader {

    public CustomClassLoader(){

    public Class loadClass(String className) throws ClassNotFoundException {
        return findClass(className);

    public Class findClass(String className){
        byte classByte[];
        Class result=null;
        result = (Class)classes.get(className);
        if(result != null){
            return result;
            String classPath = (String)ClassLoader.getSystemResource(className.replace('.',File.separatorChar)+".class").getFile();
            classByte = loadClassData(classPath);
            result = defineClass(className,classByte,0,classByte.length,null);
            return result;
        }catch(Exception e){
            return null;

    private byte[] loadClassData(String className) throws IOException{
        File f ;
        f = new File(className);
        int size = (int)f.length();
        byte buff[] = new byte[size];
        FileInputStream fis = new FileInputStream(f);
        DataInputStream dis = new DataInputStream(fis);
        return buff;

    private Hashtable classes = new Hashtable();
And the way I use it:

Java Code:
public class CustomClassLoaderTest {

    public static void main(String [] args) throws Exception{
        CustomClassLoader test = new CustomClassLoader();
        Class cHelloWorld = test.loadClass("com.octech.test.HelloWorld");