Java中List去重 爱被打了一巴掌 2022-09-08 03:53 142阅读 0赞 import java.util.ArrayList; import java.util.HashSet; import java.util.Iterator; import java.util.List; import java.util.Set; import java.util.stream.Collectors; public class Test { public static void main(String[] args) { List<String> list = new ArrayList<String>(); list.add("1001A410000000PS6PI3"); list.add("1001A410000000PS6WK7"); list.add("1001A410000000PS6PI3"); list.add("1001A410000000PS6W77"); System.out.println(removeDuplicate1(list)); // System.out.println(removeDuplicate2(list)); // System.out.println(removeDuplicate3(list)); // System.out.println(removeDuplicate4(list)); // System.out.println(removeDuplicate5(list)); } /** * 方法一: Stream 去重:list.stream().distinct() * @param list * @return */ private static List<String> removeDuplicate1(List<String> list) { List<String> newList = (List) list.stream().distinct().collect(Collectors.toList()); return newList; } /** * 方法二:通过 HashSet 剔除重复元素(会改变原有顺序) * @param list * @return */ private static List<String> removeDuplicate2(List<String> list) { Set<String> tempSet = new HashSet<String>(list); list.clear(); list.addAll(tempSet); return list; } /** * 方法三:删除 ArrayList 中重复元素,保持顺序 * @param list * @return */ private static List<String> removeDuplicate3(List<String> list) { Set<String> tempSet = new HashSet<String>(); List<String> newList = new ArrayList<>(); for (Iterator iter = list.iterator(); iter.hasNext(); ) { String next = (String) iter.next(); if (tempSet.add(next)) { newList.add(next); } } return newList; } /** * 方法四:遍历 list,用 tempList.contain(),不存在 add * @param list * @return */ private static List<String> removeDuplicate4(List<String> list) { List<String> tempList = new ArrayList<>(); for (int i = 0; i < list.size(); i++) { if (!tempList.contains(list.get(i))) { tempList.add(list.get(i)); } } return tempList; } /** * 方法五:循环 list 中的所有元素然后删除重复(会改变原有顺序) * @param list * @return */ private static List<String> removeDuplicate5(List<String> list) { for (int i = 0; i < list.size(); i++) { for (int j = list.size() - 1; j > i; j--) { if (list.get(i).equals(list.get(j))) { list.remove(list.get(i)); } } } return list; } }
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