The Arrays class is located in the java.util package and mainly includes various methods for manipulating arrays.
import java.util.Arrays;
Create a List: Arrays.asList()
List<String> list = Arrays.asList("zhangsan", "lisi", "wangwu", "sunliu");
Fill the array: Arrays.fill()
int[] arr = new int[5];//新建一个大小为5的数组
Arrays.fill(arr,4);//给所有值赋值4
int[] arr = new int[5];//新建一个大小为5的数组
Arrays.fill(arr,2,4,6);//给第2位（0开始）到第4位（不包括）赋值6
Array sorting: Arrays.sort()
The Arrays class has a static method sort. Using this method, the array to be sorted can be passed in for sorting. Because the passed in is a reference to an array, the result of sorting is also changed through this reference to change the array.
1. Number sorting
int[] intArray = new int[] {
4, 1, 3, -23 };
Arrays.sort(intArray);
2. String sorting, first uppercase and then lowercase
String[] strArray = new String[] {
“z”, “a”, “C” };
Arrays.sort(strArray);
//输出： [C, a, z]
// 严格按字母表顺序排序，也就是忽略大小写排序 Case-insensitive sort
Arrays.sort(strArray, String.CASE_INSENSITIVE_ORDER);
//输出： [a, C, z]
3. Reverse sort, Reverse-order sort
Arrays.sort(strArray, Collections.reverseOrder());
//输出：[z, a, C]
// 忽略大小写反向排序 Case-insensitive reverse-order sort
Arrays.sort(strArray, String.CASE_INSENSITIVE_ORDER);
Collections.reverse(Arrays.asList(strArray));
//输出： [z, C, a]
4. Select the specified position of the array for sorting
int[] arr = {
3,2,1,5,4};
Arrays.sort(arr,0,3);//给第0位（0开始）到第3位（不包括）排序
//输出：[1, 2, 3, 5, 4]
Print out all the contents of the array: Arrays.toString()
String str = Arrays.toString(arr); // Arrays类的toString()方法能将数组中的内容全部打印出来
//System.out.print(str);
//输出：[3, 2, 1, 5, 4]
Compare array elements for equality: Arrays.equals()
int[] arr1 = {
1,2,3};
int[] arr2 = {
1,2,3};
System.out.println(Arrays.equals(arr1,arr2));
//输出：true
//如果是arr1.equals(arr2),则返回false，因为equals比较的是两个对象的地址，不是里面的数，而Arrays.equals重写了equals，所以，这里能比较元素是否相等。
Binary search method to find the index value of the specified element: Arrays.binarySearch()
The array must be sorted, otherwise an error will occur. element found, only the last position will be returned
int[] arr = {
10,20,30,40,50};
System.out.println(Arrays.binarySearch(arr, 30));
//输出：2 （下标索引值从0开始）
int[] arr = {
10,20,30,40,50};
System.out.println(Arrays.binarySearch(arr, 36));
//输出：-4 （找不到元素，返回-x，从-1开始数，如题，返回-4）
int []arr = {
10,20,30,40,50};
System.out.println(Arrays.binarySearch(arr, 0,3,30));
//输出：2 （从0到3位（不包括）找30，找到了，在第2位，返回2）
int []arr = {
10,20,30,40,50};
System.out.println(Arrays.binarySearch(arr, 0,3,40));
//输出：-4 （从0到3位（不包括）找40，找不到，从-1开始数，返回-4）
Intercepting arrays: Arrays.copeOf() and Arrays.copeOfRange()
int[] arr = {
10,20,30,40,50};
int[] arr1 = Arrays.copyOf(arr, 3);
//输出：[10, 20, 30] （截取arr数组的3个元素赋值给新数组arr1）
int []arr = {
10,20,30,40,50};
int []arr1 = Arrays.copyOfRange(arr,1,3);;
//输出：[20, 30] （从第1位（0开始）截取到第3位（不包括））