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);
	}
	}
}