java Arrays类

java Arrays类

Arrays类概述，常用功能演示

Arrays类概述

• 数组操作工具类，专门用于操作数组元素的

Arrays类的常用API

使用实例：

/**
 * 目标：初步理解并使用Arrays提供的API接口
 * */

import java.util.Arrays;

public class ArrayDemo {
    public static void main(String[] args) {
        int[] arr = new int[]{12, 243, 4343, 43231};
        Arrays.sort(arr);

        System.out.print("[");
        for (int i = 0; i < arr.length; i++) {
            System.out.print(i != arr.length-1?(arr[i]+ ","):(arr[i]+"]"));
        }
        

        System.out.println(Arrays.toString(arr));

        System.out.println("243在数组中的索引为：" + Arrays.binarySearch(arr, 243));
    }
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22

Arrays类对于Comparator比较器的支持

自定义排序规则

• 设置Comparator接口对应的比较器对象，来定制比较规则（升序）。

如果认为左边数据大于右边数据 返回正整数

如果认为左边数据小于右边数据 返回负整数

如果认为左边数据等于右边数据 返回0

使用实例：

public class Student {
    private String name;
    private int age;
    private double height;

    public Student(String name, int age, double height) {
        this.name = name;
        this.age = age;
        this.height = height;
    }

    public Student() {
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public double getHeight() {
        return height;
    }

    public void setHeight(double height) {
        this.height = height;
    }

    @Override
    public String toString() {
        return "Student{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", height=" + height +
                '}';
    }
}

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48

import java.util.Arrays;
import java.util.Comparator;

/**
 * 目标：掌握自定义数组排列规则：Comparator比较器对象
 *
 * */

public class ArrayDemo1 {
    public static void main(String[] args) {
        Integer[] arr1 = new Integer[]{15, 3, 312, 23};
        Arrays.sort(arr1, new Comparator() {
            @Override
            public int compare(Integer o1, Integer o2) {
               // return o1 - o2;  //升序排序
                return o2 - o1;   //降序排序
            }
        });

        System.out.println(Arrays.toString(arr1));
        System.out.println("---------------------------------");

        Student[] arr2 = new Student[3];
        arr2[0] = new Student("刘备", 45, 175.4);
        arr2[1] = new Student("关羽", 35, 190.5);
        arr2[2] =new Student("张飞", 30, 185.3);
        System.out.println(Arrays.toString(arr2));

        Arrays.sort(arr2, new Comparator() {
            @Override
            public int compare(Student o1, Student o2) {
                //return o1.getAge()-o2.getAge(); //根据年龄升序排序
                //return o2.getAge()-o1.getAge(); //根据年龄降序排序
                //return Double.compare(o1.getHeight(), o2.getHeight()); //根据身高升序排序
                return Double.compare(o2.getHeight(), o1.getHeight()); //根据身高降序序排序

            }
        });

        System.out.println(Arrays.toString(arr2));
    }
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42