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)

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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);
}
}
}

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