Java中List集合去除重复数据的方法

1. 循环list中的所有元素然后删除重复

public static List removeDuplicate(List list) {
for ( int i = 0 ; i < list.size() - 1 ; i ++ ) {
for ( int j = list.size() - 1 ; j > i; j -- ) {
if (list.get(j).equals(list.get(i))) {
list.remove(j);
}
}
}
return list;
}


2. 通过HashSet踢除重复元素

public static List removeDuplicate(List list) {
HashSet h = new HashSet(list);
list.clear();
list.addAll(h);
return list;
}

3. 删除ArrayList中重复元素，保持顺序

// 删除ArrayList中重复元素，保持顺序
public static void removeDuplicateWithOrder(List list) {
Set set = new HashSet();
List newList = new ArrayList();
for (Iterator iter = list.iterator(); iter.hasNext();) {
Object element = iter.next();
if (set.add(element))
newList.add(element);
}
list.clear();
list.addAll(newList);
System.out.println( " remove duplicate " + list);
}

4.把list里的对象遍历一遍，用list.contain()，如果不存在就放入到另外一个list集合中

public static List removeDuplicate(List list){
List listTemp = new ArrayList();
for(int i=0;i<list.size();i++){
if(!listTemp.contains(list.get(i))){
listTemp.add(list.get(i));
}
}
return listTemp;
}