Added several useful classes

classpath/java/util/Comparator.java

@@ -0,0 +1,5 @@
+package java.util;
+
+public interface Comparator<T> {
+  public int compare(T o1, T o2);
+}

classpath/java/util/Date.java

@@ -0,0 +1,17 @@
+package java.util;
+
+public class Date {
+  public final long when;
+
+  public Date() {
+    when = System.currentTimeMillis();
+  }
+
+  public Date(long when) {
+    this.when = when;
+  }
+
+  public long getTime() {
+    return when;
+  }
+}