1、数组排序

        Arrays.sort(int[] a)这种形式是对一个数组的所有元素进行排序，并且是按照从小到大的排序。

        

 public static void main(String[] args) {Integer []arr = {1,2,3,4,5,6};//升序Arrays.sort(arr);for (int x:arr){System.out.print(x + " ");}System.out.println();//升序Arrays.sort(arr,new Comparator<Integer>(){@Overridepublic int compare(Integer o1,Integer o2){return o1-o2;}});for(int x:arr){System.out.print(x + " ");}System.out.println();//升序Arrays.sort(arr, (o1, o2) -> o1 - o2);for (int x:arr){System.out.print(x + " ");}System.out.println();//降序Arrays.sort(arr,new Comparator<Integer>(){@Overridepublic int compare(Integer o1,Integer o2){return o2-o1;}});for(int x:arr){System.out.print(x + " ");}System.out.println();//降序Arrays.sort(arr, (o1, o2) -> o2 - o1);for (int x:arr){System.out.print(x + " ");}}

o2 - o1 ---->  降序

o1 - o2 ----> 升序

2、集合排序

        Collections.sort(List<> arr)对一个集合的所有元素进行排序，并且按照从小到大的顺序

 

    public static void main(String[] args) {List<Integer> list = new ArrayList<>();list.add(4);list.add(5);list.add(6);list.add(3);list.add(2);list.add(1);//升序Collections.sort(list);for (int x : list){System.out.print(x + " ");}System.out.println();//升序Collections.sort(list, new Comparator<Integer>() {@Overridepublic int compare(Integer o1, Integer o2) {return o1 - o2;}});for (int i = 0; i < list.size(); i++) {System.out.print(list.get(i) + " ");}System.out.println();//升序Collections.sort(list, (o1,o2) -> o1 - o2 );for (int i = 0; i < list.size(); i++) {System.out.print(list.get(i) + " ");}System.out.println();//降序Collections.sort(list, new Comparator<Integer>() {@Overridepublic int compare(Integer o1, Integer o2) {return o2 - o1;}});for (int i = 0; i < list.size(); i++) {System.out.print(list.get(i) + " ");}System.out.println();//降序Collections.sort(list, (o1,o2) -> o2 - o1 );for (int i = 0; i < list.size(); i++) {System.out.print(list.get(i) + " ");}}