Added a hashtable that allows delayed initialization.

In most build files you don't use _all_ tasks and types -
and it takes few second to process all exceptions due to class not
found ( for optional tasks ). This class will allow tasks to
be created when needed, and will also improve the behavior
when the main class loader is changed.

PR:
Obtained from:
Submitted by:
Reviewed by:


git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@273619 13f79535-47bb-0310-9956-ffa450edef68

src/main/org/apache/tools/ant/util/LazyHashtable.java

@@ -0,0 +1,114 @@
+/*
+ * The Apache Software License, Version 1.1
+ *
+ * Copyright (c) 2000-2002 The Apache Software Foundation.  All rights
+ * reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * 3. The end-user documentation included with the redistribution, if
+ *    any, must include the following acknowlegement:
+ *       "This product includes software developed by the
+ *        Apache Software Foundation (http://www.apache.org/)."
+ *    Alternately, this acknowlegement may appear in the software itself,
+ *    if and wherever such third-party acknowlegements normally appear.
+ *
+ * 4. The names "The Jakarta Project", "Ant", and "Apache Software
+ *    Foundation" must not be used to endorse or promote products derived
+ *    from this software without prior written permission. For written
+ *    permission, please contact apache@apache.org.
+ *
+ * 5. Products derived from this software may not be called "Apache"
+ *    nor may "Apache" appear in their names without prior written
+ *    permission of the Apache Group.
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
+ * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ * ====================================================================
+ *
+ * This software consists of voluntary contributions made by many
+ * individuals on behalf of the Apache Software Foundation.  For more
+ * information on the Apache Software Foundation, please see
+ * <http://www.apache.org/>.
+ */
+package org.apache.tools.ant.util;
+
+import java.util.Hashtable;
+import java.util.Enumeration;
+
+/** Hashtable implementation that allows delayed construction
+ * of expensive objects
+ *
+ * All operations that need access to the full list of objects
+ * will call initAll() first. Get and put are cheap.
+ */
+public class LazyHashtable extends Hashtable {
+    protected boolean initAllDone=false;
+
+    public LazyHashtable() {
+        super();
+    }
+
+    /** Used to be part of init. It must be done once - but
+     * we delay it until we do need _all_ tasks. Otherwise we
+     * just get the tasks that we need, and avoid costly init.
+     */
+    protected void initAll( ) {
+        if( initAllDone ) return;
+        initAllDone=true;
+    }
+
+
+    public Enumeration elements() {
+        initAll();
+        return super.elements();
+    }
+
+    public boolean isEmpty() {
+        initAll();
+        return super.isEmpty();
+    }
+
+    public int size() {
+        initAll();
+        return super.size();
+    }
+
+    public boolean contains( Object value ) {
+        initAll();
+        return super.contains(value );
+    }
+
+    public boolean containsValue( Object value ) {
+        initAll();
+        return super.containsValue( value );
+    }
+
+    public Enumeration keys() {
+        initAll();
+        return super.keys();
+    }
+
+    // XXX Unfortunately JDK1.2 adds entrySet(), keySet(), values() -
+    // implementing this requires a small hack, we can add it later.
+}