原创： Java 删除List中的多余元素 (List 去重)

    如何去除List中重复的数据，可以使用如下的方法。
   
    注：引用的包包括：
    commons-beanutils（Bean反射工具）
    commons-lang（常用工具类，这里用到了String工具类）

package com.listutil;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

import org.apache.commons.beanutils.BeanUtils;
import org.apache.commons.lang.StringUtils;

import com.Sort.BeanSort.TestBean;

/**
 * List Utilities
 * 
 * @author Michael Leo
 * @since 2010/05/20
 */
public class ListUtils
{
	private static final char SEPARATOR = '|';

	/**
	 * Remove the duplicate element in List according to the specified keys in
	 * List bean and return a new list.</br>
	 * 
	 * If the parameters are empty or exception occurred, original list will be
	 * returned.
	 * 
	 * @param list
	 *            To be processed list
	 * @param keys
	 *            The fields in List bean as keys
	 * @return
	 */
	public static <T> List<T> removeDuplication(List<T> list, String... keys)
	{
		if (list == null || list.isEmpty())
		{
			System.err.println("List is empty.");
			return list;
		}

		if (keys == null || keys.length < 1)
		{
			System.err.println("Missing parameters.");
			return list;
		}

		for (String key : keys)
		{
			if (StringUtils.isBlank(key))
			{
				System.err.println("Key is empty.");
				return list;
			}
		}

		List<T> newList = new ArrayList<T>();
		Set<String> keySet = new HashSet<String>();

		for (T t : list)
		{
			StringBuffer logicKey = new StringBuffer();
			for (String keyField : keys)
			{
				try
				{
					logicKey.append(BeanUtils.getProperty(t, keyField));
					logicKey.append(SEPARATOR);
				}
				catch (Exception e)
				{
					e.printStackTrace();
					return list;
				}
			}
			if (!keySet.contains(logicKey.toString()))
			{
				keySet.add(logicKey.toString());
				newList.add(t);
			}
			else
			{
				System.err.println(logicKey + " has duplicated.");
			}
		}

		return newList;
	}

	public static void main(String[] args)
	{
		List<TestBean> list = new ArrayList<TestBean>();

		TestBean tb1 = new TestBean();
		tb1.setField1(34);
		tb1.setField3("aaa");

		TestBean tb2 = new TestBean();
		tb2.setField1(344);
		tb2.setField3("ab");

		TestBean tb3 = new TestBean();
		tb3.setField1(3344);
		tb3.setField3("ab");

		TestBean tb4 = new TestBean();
		tb4.setField1(3344);
		tb4.setField3("ab");

		list.add(tb1);
		list.add(tb2);
		list.add(tb3);
		list.add(tb4);

		List<TestBean> list2 = removeDuplication(list, "field1", "field3");

		for (TestBean b : list)
		{
			System.out.println(b);
		}
		System.out.println("---------------------");
		for (TestBean b : list2)
		{
			System.out.println(b);
		}
	}
}