more classpath classes

classpath/java/util/HashSet.java

@@ -0,0 +1,55 @@
+package java.util;
+
+public class HashSet<T> implements Set<T> {
+  private static final Object Value = new Object();
+
+  private final HashMap<T, Object> map;
+
+  public HashSet(int capacity) {
+    map = new HashMap(capacity);
+  }
+
+  public HashSet() {
+    this(0);
+  }
+
+  public int size() {
+    return map.size();
+  }
+
+  public boolean add(T element) {
+    return map.put(element, Value) != Value;
+  }
+
+  public boolean remove(T element) {
+    return map.remove(element) != Value;
+  }
+
+  public void clear() {
+    map.clear();
+  }
+
+  public Iterator<T> iterator() {
+    return new MyIterator(map.iterator());
+  }
+
+  private static class MyIterator<T> implements Iterator<T> {
+    private final Iterator<Map.Entry<T, Object>> it;
+
+    public MyIterator(Iterator<Map.Entry<T, Object>> it) {
+      this.it = it;
+    }
+
+    public T next() {
+      return it.next().getKey();
+    }
+
+    public boolean hasNext() {
+      return it.hasNext();
+    }
+
+    public void remove() {
+      it.remove();
+    }
+  }
+}