[120] | 1 | /** |
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| 2 | * Licensed to the Apache Software Foundation (ASF) under one |
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| 3 | * or more contributor license agreements. See the NOTICE file |
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| 4 | * distributed with this work for additional information |
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| 5 | * regarding copyright ownership. The ASF licenses this file |
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| 6 | * to you under the Apache License, Version 2.0 (the |
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| 7 | * "License"); you may not use this file except in compliance |
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| 8 | * with the License. You may obtain a copy of the License at |
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| 9 | * |
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| 10 | * http://www.apache.org/licenses/LICENSE-2.0 |
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| 11 | * |
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| 12 | * Unless required by applicable law or agreed to in writing, software |
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| 13 | * distributed under the License is distributed on an "AS IS" BASIS, |
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| 14 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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| 15 | * See the License for the specific language governing permissions and |
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| 16 | * limitations under the License. |
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| 17 | */ |
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| 18 | |
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| 19 | package org.apache.hadoop.util; |
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| 20 | |
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| 21 | import java.lang.reflect.Array; |
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| 22 | import java.util.List; |
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| 23 | |
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| 24 | /** |
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| 25 | * Contains utility methods for dealing with Java Generics. |
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| 26 | */ |
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| 27 | public class GenericsUtil { |
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| 28 | |
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| 29 | /** |
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| 30 | * Returns the Class object (of type <code>Class<T></code>) of the |
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| 31 | * argument of type <code>T</code>. |
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| 32 | * @param <T> The type of the argument |
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| 33 | * @param t the object to get it class |
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| 34 | * @return <code>Class<T></code> |
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| 35 | */ |
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| 36 | public static <T> Class<T> getClass(T t) { |
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| 37 | @SuppressWarnings("unchecked") |
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| 38 | Class<T> clazz = (Class<T>)t.getClass(); |
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| 39 | return clazz; |
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| 40 | } |
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| 41 | |
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| 42 | /** |
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| 43 | * Converts the given <code>List<T></code> to a an array of |
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| 44 | * <code>T[]</code>. |
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| 45 | * @param c the Class object of the items in the list |
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| 46 | * @param list the list to convert |
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| 47 | */ |
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| 48 | public static <T> T[] toArray(Class<T> c, List<T> list) |
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| 49 | { |
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| 50 | @SuppressWarnings("unchecked") |
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| 51 | T[] ta= (T[])Array.newInstance(c, list.size()); |
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| 52 | |
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| 53 | for (int i= 0; i<list.size(); i++) |
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| 54 | ta[i]= list.get(i); |
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| 55 | return ta; |
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| 56 | } |
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| 57 | |
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| 58 | |
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| 59 | /** |
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| 60 | * Converts the given <code>List<T></code> to a an array of |
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| 61 | * <code>T[]</code>. |
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| 62 | * @param list the list to convert |
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| 63 | * @throws ArrayIndexOutOfBoundsException if the list is empty. |
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| 64 | * Use {@link #toArray(Class, List)} if the list may be empty. |
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| 65 | */ |
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| 66 | public static <T> T[] toArray(List<T> list) { |
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| 67 | return toArray(getClass(list.get(0)), list); |
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| 68 | } |
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| 69 | |
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| 70 | } |
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