How to use Arrays class in Java?

1. Description

This class contains various methods used to operate on arrays (such as sorting and searching). This class also contains a static factory that allows the array to be viewed as a list.

Unless otherwise noted, if the specified array reference is null, the methods in this class will throw NullPointerException.

2. Commonly used methods

Assign a value to the array: fill method

Sort the array:The sort method compares the array in ascending order

: The equals method compares whether the element values ​​in the array are equal.

Search for array elements: The binarySearch method can perform a binary search operation on the array of sort numbers.

3. Example

public static void main(String[] args) {
// TODO Auto-generated method stub
 
int[] a=new int[10];  
Arrays.fill(a, 5);        //Arrays自带的填充函数
System.out.println(Arrays.toString(a));   //不能直接输出a.toString(),会有乱码！
for(int i=0;i<a.length;++i)
{
a[i]=i*2;
}
int[] b=Arrays.copyOf(a, 12);     //够了就截断，不够就补零
System.out.println(Arrays.toString(b));
int[] c=Arrays.copyOfRange(b, 0, 12);   //当然，也可以自定义选择的范围
System.out.println(Arrays.toString(c));
System.out.println(Arrays.binarySearch(b, 0)); //查找到第一个目标数的index，否则返回-1.
Arrays.sort(b);         //排序，默认升序排列
System.out.println(Arrays.toString(b));
if(!Arrays.equals(c, b))      //判断两数组是否相等,且这个判断是和顺序相关的！仅当元素一直且顺序一致时才返回true！
System.out.println("c != b");
else
System.out.println("c == b");
List<int[]> list=Arrays.asList(a);    //collections和arrays之间的转换！后续将深入讨论！
}
 
//OUTPUT
[5, 5, 5, 5, 5, 5, 5, 5, 5, 5]
[0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 0, 0]
[0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 0, 0]
0
[0, 0, 0, 2, 4, 6, 8, 10, 12, 14, 16, 18]
c != b

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