An iterator that iterates over the union of the iterators provided by a

collection of collections.


git-svn-id: https://samskivert.googlecode.com/svn/trunk@893 6335cc39-0255-0410-8fd6-9bcaacd3b74c

projects/samskivert/src/java/com/samskivert/util/IteratorIterator.java

@@ -0,0 +1,63 @@
+//
+// $Id: IteratorIterator.java,v 1.1 2002/11/07 05:58:31 mdb Exp $
+
+package com.samskivert.util;
+
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+
+/**
+ * An iterator that can iterate over the elements in several collections
+ * contained within a master collection.
+ */
+public class IteratorIterator implements Iterator
+{
+    /**
+     * @param collections a Collection containing more Collections
+     * whose elements we are to iterate over.
+     */
+    public IteratorIterator (Collection collections)
+    {
+        _meta = collections.iterator();
+    }
+
+    // documentation inherited from interface Iterator
+    public boolean hasNext ()
+    {
+        while ((_current == null) || (!_current.hasNext())) {
+            if (_meta.hasNext()) {
+                _current = ((Collection) _meta.next()).iterator();
+            } else {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    // documentation inherited from interface Iterator
+    public Object next ()
+    {
+        if (hasNext()) {
+            return _current.next();
+        } else {
+            throw new NoSuchElementException();
+        }
+    }
+
+    // documentation inherited from interface Iterator
+    public void remove ()
+    {
+        if (_current != null) {
+            _current.remove();
+        } else {
+            throw new IllegalStateException();
+        }
+    }
+
+    /** The iterator through the collection we were constructed with. */
+    protected Iterator _meta;
+
+    /** The current sub-collection's iterator. */
+    protected Iterator _current;
+}