数组

2020-08-07 阅读量

数组的定义

数组是相同类型数据的有序集合。

数组变量属于引用类型，数组也可以看做是对象，数组中的每个元素相当于该对象的成员变量

package cn.yishan.arrays;

public class Test01 {
    public static void main(String[] args) {
        int[] arr01 = new int[10];
        String[] arr02 = new String[5];
        User[] arr03 = new User[3];

        arr01[0] = 13;
        arr01[1] = 15;
        arr01[2] = 20;
        for (int i = 0;i < arr01.length;i++){

            arr01[i] = 10 * i;
        }
        for (int i = 0;i < arr01.length;i++ ){
            System.out.println(arr01[i]);
        }

        arr03[0] = new User(1001,"亦山");
        arr03[1] = new User(1002,"哈哈");
        arr03[2] = new User(1003,"呵呵");

        for (int i = 0;i < arr03.length;i++){
            System.out.println(arr03[i].getName()+"---"+ arr03[i].getId());
        }
    }


}

class User{
    private int id ;
    private String name;

    public User(int id, String name) {
        this.id = id;
        this.name = name;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

数组的初始化

包括：动态初始化，静态初始化，默认初始化

测试数组的三种初始化方式
package cn.yishan.arrays;

public class Test02 {
    public static void main(String[] args) {
        //静态初始化
        int[] a = {2,4,65};
        User[] b = {new User(1001,"杨"),
                new User(1002,"亦"),
                new User(1003,"山")
        };
        //默认初始化,默认给数组的元素进行赋值。赋值的规则和成员变量的赋值规则一致
        int[] c = new int[3];
        //动态初始化
        int[] a1 = new int [2];//动态初始化数组，先分配空间；
        a1[0] = 1;//给数组元素赋值
        a1[2] = 2;//给数组元素赋值 
    }

}

数组的遍历，foreach循环

测试数组的遍历
package cn.yishan.arrays;

public class Test03 {
    public static void main(String[] args) {
        int[] a = new int[4];
        //初始化数组元素的值
        for (int i = 0;i < a.length;i++){
            a[i] = 100*i;
        }
        //读取元素的值
        for (int i = 0;i < a.length;i++){
            System.out.println(a[i]);
        }
        //foreach循环：用于读取数组元素的值，不能修改数组元素的值
        for (int m : a){
            System.out.println(m);
        }
    }
}