构造函数重载示例中的混淆

Question

以下程序将输出作为

 I am Parameterized Ctor
 a = 0
 b = 0

---

public class ParameterizedCtor {

    private int a;
    private int b;

    public ParameterizedCtor() {
        System.out.println("I am default Ctor");
        a =1;
        b =1;
    }

    public ParameterizedCtor(int a, int b) {
        System.out.println(" I am Parameterized Ctor");
        a=a;
        b=b;

    }
    public void print() {
        System.out.println(" a = "+a);
        System.out.println(" b = "+b);
    }

    public static void main(String[] args) {

        ParameterizedCtor c = new ParameterizedCtor(3, 1);
        c.print();
    }

}

是什么原因？

Answer 1

默认情况下,未初始化的私有变量a和b设置为零.并且重载c'tctor到位.我将从main调用parameterCtor(int a,int b),并且局部变量a和b设置为3和1,但类变量a和b仍为零.因此,a = 0,b = 0(不会调用默认的c'tor).

要设置类变量,请使用:

this.a = a;
this.b = b;

Answer 2

你需要这样做:

public ParameterizedCtor(int a, int b) {
    System.out.println(" I am Parameterized Ctor");
    this.a=a;
    this.b=b;
}

否则,您只需将参数a和b参数重新分配给自己.