java中List数组遍历删除

Kent_Sun 38 0 0

List数组遍历删除

环境

  • jdk8
  • junit 单元测试

正解

// 正解1, jdk自带的addAll方法
    @Test
    public void test18() {
        String[] strs = {"12","34","56","78","90"};
        List<String> list = Arrays.asList(strs);
        List<String> list2 = new ArrayList<>();
        list2.addAll(list);
        System.out.println(list);
        for (String s : list) {
            System.out.println(s);
            list2.remove(s);
        }
    }

// 正解2 Hutool的 CollUtil 工具类中addAll方法
    @Test
    public void test18() {
        String[] strs = {"12","34","56","78","90"};
        List<String> list = Arrays.asList(strs);
        List<String> list2 = new ArrayList<>();
        CollUtil.addAll(list2,list);
        System.out.println(list2);
        for (String s : list) {
            System.out.println(s);
            list2.remove(s);
        }
    }

boolean b = list1.removeIf(a -> (a % 2) == 0);
        System.out.println(b);

错解

新手代码踩坑日记

// 第一错
    @Test
    public void test18() {
         String[] strs = {"12","34","56","78","90"};
         List<String> list = Arrays.asList(strs);
         System.out.println(list);
         for (String s : list) {
             System.out.println(s);
             list.remove(s);
         }
    }

报错信息:

[12, 34, 56, 78, 90]
12

java.lang.UnsupportedOperationException  不支持的操作异常
    at java.util.AbstractList.remove(AbstractList.java:161)
    at java.util.AbstractList$Itr.remove(AbstractList.java:374)
    at java.util.AbstractCollection.remove(AbstractCollection.java:293)


// 第二错 : 老子新建个对象来存还是错??? 仔细想想-->TMD谁写的垃圾代码,好像是我写的...
// 方法栈里面就一个list对象,只是复制一份引用,而remove是直接操作数组内存空间
     @Test
    public void test18() {
        String[] strs = {"12","34","56","78","90"};
        List<String> list = Arrays.asList(strs);
        List<String> list2 = new ArrayList<>();
        list2 = list;
        System.out.println(list);
        for (String s : list) {
            System.out.println(s);
            list2.remove(s);
        }
    }

直接报错 +1:
[12, 34, 56, 78, 90]
12

java.lang.UnsupportedOperationException
    at java.util.AbstractList.remove(AbstractList.java:161)
    at java.util.AbstractList$Itr.remove(AbstractList.java:374)
    at java.util.AbstractCollection.remove(AbstractCollection.java:293)
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