add basic URLClassLoader implementation

classpath/java/net/URLClassLoader.java

@@ -0,0 +1,57 @@
+package java.net;
+
+import java.io.File;
+
+import java.io.InputStream;
+import java.io.IOException;
+import java.io.ByteArrayOutputStream;
+
+public class URLClassLoader extends ClassLoader {
+
+  private final File jarFile;
+
+  public URLClassLoader(URL[] urls, ClassLoader parent) {
+    super(parent);
+    if(urls.length != 1) {
+      throw new UnsupportedOperationException();
+    }
+    if(!urls[0].getProtocol().equals("file")) {
+      throw new UnsupportedOperationException(urls[0].getProtocol());
+    }
+    this.jarFile = new File(urls[0].getFile());
+  }
+
+
+  protected Class findClass(String name) throws ClassNotFoundException {
+    try {
+      InputStream stream = getResourceAsStream(name.replace(".", "/") + ".class");
+      if(stream == null) {
+        throw new ClassNotFoundException("couldn't find class " + name);
+      }
+      byte[] buf = new byte[2048];
+      ByteArrayOutputStream mem = new ByteArrayOutputStream();
+      try {
+        int size;
+        while((size = stream.read(buf, 0, buf.length)) > 0) {
+          mem.write(buf, 0, size);
+        }
+        byte[] data = mem.toByteArray();
+        return defineClass(name, data, 0, data.length);
+      } finally {
+        stream.close();
+      }
+    } catch(IOException e) {
+      throw new ClassNotFoundException("couldn't find class " + name, e);
+    }
+  }
+
+  public URL getResource(String path) {
+    try {
+      return new URL("jar:file:" + jarFile.getAbsolutePath() + "!/" + path);
+    } catch(MalformedURLException e) {
+      throw new RuntimeException(e);
+    }
+  }
+
+
+}