Collections常用方法总结

Posted 2020-10-10

public class CollectionsTest {

    public static void main(String[] args) {
        List<Integer> list = new ArrayList<Integer>();
        list.add(34);
        list.add(55);
        list.add(56);
        list.add(89);
        list.add(12);
        list.add(23);
        list.add(126);
        System.out.println(list);

        //对集合进行排序
        Collections.sort(list);
        System.out.println(list);

        //对集合进行随机排序
        Collections.shuffle(list);
        System.out.println(list);

        //获取集合最大值、最小值
        int max = Collections.max(list);
        int min = Collections.min(list);
        System.out.println("Max:" + max + " Min: " + min);

        List<String> list2 = Arrays.asList("Monday,Tuesday,Wednesday,Thursday,Friday,Saturday,Sunday".split(","));
        System.out.println(list2);

        //查找集合指定元素，返回元素所在索引
        //若元素不存在，n表示该元素最有可能存在的位置索引
        int index1 = Collections.binarySearch(list2, "Thursday");
        int index2 = Collections.binarySearch(list2, "TTTTTT");
        System.out.println(index1);
        int n = -index2 - 1;

        //查找子串在集合中首次出现的位置
        List<String> subList = Arrays.asList("Friday,Saturday".split(","));
        int index3 = Collections.indexOfSubList(list2, subList);
        System.out.println(index3);
        int index4 = Collections.lastIndexOfSubList(list2, subList);
        System.out.println(index4);

        //替换集合中指定的元素，若元素存在返回true，否则返回false
        boolean flag = Collections.replaceAll(list2, "Sunday", "tttttt");
        System.out.println(flag);
        System.out.println(list2);

        //反转集合中的元素的顺序
        Collections.reverse(list2);
        System.out.println(list2);

        //集合中的元素向后移动k位置，后面的元素出现在集合开始的位置
        Collections.rotate(list2, 3);
        System.out.println(list2);

        //将集合list3中的元素复制到list2中，并覆盖相应索引位置的元素
        List<String> list3 = Arrays.asList("copy1,copy2,copy3".split(","));
        Collections.copy(list2, list3);
        System.out.println(list2);

        //交换集合中指定元素的位置
        Collections.swap(list2, 0, 3);
        System.out.println(list2);

        //替换集合中的所有元素，用对象object
        Collections.fill(list2, "替换");
        System.out.println(list2);

        //生成一个指定大小与内容的集合
        List<String> list4 = Collections.nCopies(5, "哈哈");
        System.out.println(list4);

        //为集合生成一个Enumeration
        List<String> list5 = Arrays.asList("I love my country!".split(" "));
        System.out.println(list5);
        Enumeration<String> e = Collections.enumeration(list5);
        while (e.hasMoreElements()) {
            System.out.println(e.nextElement());
        }
    }
}