hadoop GenericsUtil 源码

haddop GenericsUtil 代码

文件路径：/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/GenericsUtil.java

/**
 * 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;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Contains utility methods for dealing with Java Generics. 
 */
@InterfaceAudience.Private
@InterfaceStability.Unstable
public class GenericsUtil {

  /**
   * Returns the Class object (of type <code>Class&lt;T&gt;</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&lt;T&gt;</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&lt;T&gt;</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
   * @param <T> Generics Type T.
   * @return T Array.
   */
  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&lt;T&gt;</code> to a an array of 
   * <code>T[]</code>. 
   * @param list the list to convert
   * @param <T> Generics Type T.
   * @throws ArrayIndexOutOfBoundsException if the list is empty. 
   * Use {@link #toArray(Class, List)} if the list may be empty.
   * @return T Array.
   */
  public static <T> T[] toArray(List<T> list) {
    return toArray(getClass(list.get(0)), list);
  }

  /**
   * Determine whether the log of <code>clazz</code> is Log4j implementation.
   * @param clazz a class to be determined
   * @return true if the log of <code>clazz</code> is Log4j implementation.
   */
  public static boolean isLog4jLogger(Class<?> clazz) {
    if (clazz == null) {
      return false;
    }
    Logger log = LoggerFactory.getLogger(clazz);
    try {
      Class log4jClass = Class.forName("org.slf4j.impl.Log4jLoggerAdapter");
      return log4jClass.isInstance(log);
    } catch (ClassNotFoundException e) {
      return false;
    }
  }
}

相关信息

hadoop 源码目录

相关文章

hadoop ApplicationClassLoader 源码

hadoop AsyncDiskService 源码

hadoop AutoCloseableLock 源码

hadoop BasicDiskValidator 源码

hadoop BlockingThreadPoolExecutorService 源码

hadoop CacheableIPList 源码

hadoop ChunkedArrayList 源码

hadoop ClassUtil 源码

hadoop Classpath 源码

hadoop CleanerUtil 源码