List 集合去除重复元素的5种方法

目录

1、for循环添加去重

2、for 双循环去重

3、for 双循环重复坐标去重

4、Set去重

5、stream流去重

---

1、for循环添加去重

    List<String> oldList = new ArrayList<>();
        oldList.add("张三");
        oldList.add("张三");
        oldList.add("李四");
        oldList.add("王五");
        oldList.add("赵六");
        List<Object> newList = Lists.newArrayList();
        for (String name : oldList) {
            if (!newList.contains(name)){
                newList.add(name);
            }
        }
        System.out.println("原本的集合原素"+oldList);
        System.out.println("去重后的集合"+newList);

打印结果如下：

2、for 双循环去重

    @Test
    void contextLoads3() {
        List<String> oldList = new ArrayList<>();
        oldList.add("张三");
        oldList.add("张三");
        oldList.add("李四");
        oldList.add("王五");
        oldList.add("赵六");
        for (int i = 0; i < oldList.size() - 1; i++) {
            for (int j = oldList.size() - 1; j>1 ; j--) {
                if (oldList.get(j).equals(oldList.get(i))) {
                    oldList.remove(j);
                }
            }
        }
        System.out.println("原本的集合原素"+oldList);
    }

打印结果如下：

3、for 双循环重复坐标去重

   @Test
    void contextLoads4() {
        List<String> oldList = new ArrayList<>();
        oldList.add("张三");
        oldList.add("张三");
        oldList.add("李四");
        oldList.add("王五");
        oldList.add("赵六");
        List<String> newList = Lists.newArrayList();
        newList.addAll(oldList);
        for (String name : newList) {
            if (oldList.indexOf(name) != oldList.lastIndexOf(name)) {
                oldList.remove(oldList.lastIndexOf(name));
            }
        }
        System.out.println("原本的集合原素"+oldList);
    }

打印结果如下：

4、Set去重

    @Test
    void contextLoads5() {
        List<String> oldList = new ArrayList<>();
        oldList.add("张三");
        oldList.add("张三");
        oldList.add("李四");
        oldList.add("王五");
        oldList.add("赵六");
        List<String> newList = Lists.newArrayList(new HashSet(oldList));
        System.out.println("原本的集合原素"+newList);
    }

打印结果如下：

5、stream流去重

    @Test
    void contextLoads5() {
        List<String> oldList = new ArrayList<>();
        oldList.add("张三");
        oldList.add("张三");
        oldList.add("李四");
        oldList.add("王五");
        oldList.add("赵六");
        List<String> collect = oldList.stream().distinct().collect(Collectors.toList());
        System.out.println("原本的集合原素"+collect);
    }

打印结果如下：