| /** |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package org.apache.hadoop.util; |
| |
| import java.lang.reflect.Array; |
| import java.util.List; |
| |
| import org.apache.hadoop.classification.InterfaceAudience; |
| import org.apache.hadoop.classification.InterfaceStability; |
| |
| /** |
| * Contains utility methods for dealing with Java Generics. |
| */ |
| @InterfaceAudience.Private |
| @InterfaceStability.Unstable |
| public class GenericsUtil { |
| |
| /** |
| * Returns the Class object (of type <code>Class<T></code>) of the |
| * argument of type <code>T</code>. |
| * @param <T> The type of the argument |
| * @param t the object to get it class |
| * @return <code>Class<T></code> |
| */ |
| public static <T> Class<T> getClass(T t) { |
| @SuppressWarnings("unchecked") |
| Class<T> clazz = (Class<T>)t.getClass(); |
| return clazz; |
| } |
| |
| /** |
| * Converts the given <code>List<T></code> to a an array of |
| * <code>T[]</code>. |
| * @param c the Class object of the items in the list |
| * @param list the list to convert |
| */ |
| public static <T> T[] toArray(Class<T> c, List<T> list) |
| { |
| @SuppressWarnings("unchecked") |
| T[] ta= (T[])Array.newInstance(c, list.size()); |
| |
| for (int i= 0; i<list.size(); i++) |
| ta[i]= list.get(i); |
| return ta; |
| } |
| |
| |
| /** |
| * Converts the given <code>List<T></code> to a an array of |
| * <code>T[]</code>. |
| * @param list the list to convert |
| * @throws ArrayIndexOutOfBoundsException if the list is empty. |
| * Use {@link #toArray(Class, List)} if the list may be empty. |
| */ |
| public static <T> T[] toArray(List<T> list) { |
| return toArray(getClass(list.get(0)), list); |
| } |
| |
| } |