java中如何像go一样实现结构体嵌套,达到嵌套对象的元素冒泡到外层?

Question

如下是我在go中经常用到的特性, 它可以冒泡结构体元素到上一层:

package mainimport "fmt"import "encoding/json"type A struct {    Ax, ay int}type B struct {    A    Bx, by float32}func main() {    b := B{A{1, 2}, 3.0, 4.0}    bytes, _ := json.Marshal(b)    fmt.Println(string(bytes))}

output:

{"Ax":1,"Bx":3}

这个东西有什么用?

遍历持久化数据到A上, 然后在A的基础上附加Bx属性

java我知道有匿名内部类, 但是我想知道如何做到这样的结果?

Answer 1

Java中的类是不能直接嵌套的，不过可以模拟一下：

public class OuterClass {    private InnerClass innerClass;    private float Bx;    private float by;    public OuterClass(int Ax, int ay, float Bx, float by) {        this.innerClass = new InnerClass(Ax, ay);        this.Bx = Bx;        this.by = by;    }    public int getAx() {        return innerClass.getAx();    }    public float getBx() {        return Bx;    }    private class InnerClass {        private int Ax;        private int ay;        public InnerClass(int Ax, int ay) {            this.Ax = Ax;            this.ay = ay;        }        public int getAx() {            return Ax;        }    }}

用继承java里：

class A {    public int Ax;    private int ay;    // getters and setters}class B extends A {    public float Bx;    private float by;    // getters and setters}public class Main {    public static void main(String[] args) {        B b = new B();        b.Ax = 1;        b.Bx = 3.0f;        System.out.println("Ax: " + b.Ax + ", Bx: " + b.Bx);    }}