add a few classpath methods

classpath/java/lang/String.java

@@ -1,5 +1,7 @@
 package java.lang;
 
+import java.io.UnsupportedEncodingException;
+
 public final class String implements Comparable<String> {
   private Object data;
   private int offset;
@@ -30,6 +32,15 @@ public final class String implements Comparable<String> {
     this(data, 0, data.length);
   }
 
+  public String(byte[] data, String charset)
+    throws UnsupportedEncodingException
+  {
+    this(data);
+    if (! charset.equals("US-ASCII")) {
+      throw new UnsupportedEncodingException(charset);
+    }
+  }
+
   private String(Object data, int offset, int length, boolean copy) {
     int l;
     if (data instanceof char[]) {

classpath/java/lang/Thread.java

@@ -29,6 +29,10 @@ public class Thread implements Runnable {
     classLoader = current.classLoader;
   }
 
+  public Thread(Runnable task, String name) {
+    this(task);
+  }
+
   public synchronized void start() {
     if (peer != 0) {
       throw new IllegalStateException("thread already started");

classpath/java/util/Collection.java

@@ -3,6 +3,8 @@ package java.util;
 public interface Collection<T> extends Iterable<T> {
   public int size();
 
+  public boolean isEmpty();
+
   public boolean contains(T element);
 
   public boolean add(T element);