1 files changed, 79 insertions, 0 deletions
diff --git a/plugins/org.eclipse.net4j.util/src/org/eclipse/net4j/util/collection/AbstractIterator.java b/plugins/org.eclipse.net4j.util/src/org/eclipse/net4j/util/collection/AbstractIterator.java
new file mode 100644
index 0000000000..897a487bb0
--- /dev/null
+++ b/plugins/org.eclipse.net4j.util/src/org/eclipse/net4j/util/collection/AbstractIterator.java
@@ -0,0 +1,79 @@
+/*
+ * Copyright (c) 2004 - 2011 Eike Stepper (Berlin, Germany) and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *    Eike Stepper - initial API and implementation
+ */
+package org.eclipse.net4j.util.collection;
+
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+
+/**
+ * An abstract base class for custom iterators that only requires to implement a single {@link #computeNextElement()}
+ * method.
+ * 
+ * @author Eike Stepper
+ * @since 3.2
+ */
+public abstract class AbstractIterator<T> implements Iterator<T>
+{
+  /**
+   * The token to be used in {@link #computeNextElement()} to indicate the end of the iteration.
+   */
+  protected static final Object END_OF_DATA = new Object();
+
+  private boolean computed;
+
+  private T next;
+
+  public AbstractIterator()
+  {
+  }
+
+  public final boolean hasNext()
+  {
+    if (computed)
+    {
+      return true;
+    }
+
+    Object object = computeNextElement();
+    computed = true;
+
+    if (object == END_OF_DATA)
+    {
+      return false;
+    }
+
+    @SuppressWarnings("unchecked")
+    T cast = (T)object;
+    next = cast;
+    return true;
+  }
+
+  public final T next()
+  {
+    if (!hasNext())
+    {
+      throw new NoSuchElementException();
+    }
+
+    computed = false;
+    return next;
+  }
+
+  public void remove()
+  {
+    throw new UnsupportedOperationException();
+  }
+
+  /**
+   * Returns the next iteration element, or {@link #END_OF_DATA} if the end of the iteration has been reached.
+   */
+  protected abstract Object computeNextElement();
+}