JavaSE 14 Arrays array utility class

Chapter 19 Arrays Array Tool Class

19.1 Overview:

• java.util.Arrays is a tool class related to arrays, which provides a large number of static methods to implement common operations on arrays.

19.2 Program an array of parameters to a string

Output format: [element1, element2, ...]

public static String toString(数组)

import java.util.Arrays;

public class DemoArrays {
    
    

    public static void main(String[] args) {
    
    
        int[] intArr = {
    
     1, 2, 3 };
        String intStr = Arrays.toString(intArr);
        System.out.println(intStr);//[1, 2, 3]
    }

}

19.3 Sorting the parameter array

• Sorts the elements of the array in the default ascending order.

1. If it is a value, sort defaults to ascending order from small to large
2. If it is a string, sort defaults to ascending alphabetical order
3. If it is a custom type, then this custom class needs to be supported by the Comparable or Comparator interface.

public static void sort(数组)

import java.util.Arrays;

public class DemoArrays {
    
    

    public static void main(String[] args) {
    
    
        int[] array = {
    
     2, 1, 3, 6, 8 };
        Arrays.sort(array);
        System.out.println(Arrays.toString(array));//[1, 2, 3, 6, 8]
    }

}

19.4 Exercises

import java.util.Arrays;

/*
将一个随机字符串中的所有字符升序排列，并且倒序打印
 */
public class Demo03ArraysTest {
    
    

    public static void main(String[] args) {
    
    
        String str = "asdiugfrqgbbvwierhisdf";
        char[] chars = str.toCharArray();
        Arrays.sort(chars);

		//IDEA快捷输入chars.forr
        for (int i = chars.length - 1; i >= 0; i--) //反向遍历打印
            System.out.print(chars[i] + " ");
        }
    }

}