import java.net.URL;
import java.net.URLClassLoader;
import java.util.Map;

public final class MemoryClassLoader extends URLClassLoader {
    private final Map<String, byte[]> classBytes;

    public MemoryClassLoader(Map<String, byte[]> classBytes) {
        super(new URL[]{});
        this.classBytes = classBytes; 
    }

    @Override
    protected Class findClass(String className) throws ClassNotFoundException {
        byte[] buf = classBytes.get(className);
        if (buf != null) {
            classBytes.put(className, null);
            return defineClass(className, buf, 0, buf.length);
        } else {
            return super.findClass(className);
        }
    }
}