Publish

1 files changed, 75 insertions, 0 deletions

diff --git a/vespajlib/src/main/java/com/yahoo/collections/ListenableArrayList.java b/vespajlib/src/main/java/com/yahoo/collections/ListenableArrayList.java
new file mode 100644
index 00000000000..1b77e97d159
--- /dev/null
+++ b/vespajlib/src/main/java/com/yahoo/collections/ListenableArrayList.java
@@ -0,0 +1,75 @@
+// Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.collections;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+
+/**
+ * An array list which notifies listeners after one or more items are added
+ *
+ * @author <a href="mailto:bratseth@yahoo-inc.com">Jon Bratseth</a>
+ * @since 5.1.17
+ */
+@SuppressWarnings("serial")
+public class ListenableArrayList<ITEM> extends ArrayList<ITEM> {
+
+    private List<Runnable> listeners = null;
+
+    public ListenableArrayList() {}
+
+    public ListenableArrayList(int initialCapacity) {
+        super(initialCapacity);
+    }
+
+    @Override
+    public boolean add(ITEM e) {
+        boolean result = super.add(e);
+        notifyListeners();
+        return result;
+    }
+
+    @Override
+    public void add(int index, ITEM e) {
+        super.add(index, e);
+        notifyListeners();
+    }
+
+    @Override
+    public boolean addAll(Collection<? extends ITEM> a) {
+        boolean result = super.addAll(a);
+        notifyListeners();
+        return result;
+    }
+
+    @Override
+    public boolean addAll(int index, Collection<? extends ITEM> a) {
+        boolean result = super.addAll(index, a);
+        notifyListeners();
+        return result;
+    }
+
+    @Override
+    public ITEM set(int index, ITEM e) {
+        ITEM result = super.set(index, e);
+        notifyListeners();
+        return result;
+    }
+
+    /**
+     * Adds a listener which is invoked whenever elements are added to this.
+     * This may not be invoked once for each added element.
+     */
+    public void addListener(Runnable listener) {
+        if (listeners == null)
+            listeners = new ArrayList<>();
+        listeners.add(listener);
+    }
+
+    private void notifyListeners() {
+        if (listeners == null) return;
+        for (Runnable listener : listeners)
+            listener.run();
+    }
+
+}