java基础 javaBean对象成员变量默认值及数组默认值

Posted 2021-01-24 1314520jinxuexia

public class StudentTest {
    private int id;
    private String name;
    int[] arr;

    public int[] getArr() {
        return arr;
    }

    public void setArr(int[] arr) {
        this.arr = arr;
    }

    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;
    }
}

public class guanxiaokun {
    public static void main(String[] args) {
        //对于javaBean对象的成员变量,都有默认值,如果成员变量是基本类型int 默认值为0,如果是引用类型,其默认值为null
        //数组对象,如果没有进行静态初始化,数组对象其每一个索引位置,如果是存储基本类型,默认值为0,如果存储引用类型,默认值就为null
        System.out.println(new StudentTest().getId());//0
        System.out.println(new StudentTest().getName());//null
        System.out.println(new StudentTest().getArr());//null
        int[] arr = new int[3]; 
        String[] str = new String[3];
        System.out.println(arr[0]);//0
        System.out.println(str[0]);//null
    }
}