using a variable in constructor in a method outsid

问题:

if i have a constructor like so:

    public Constructor (int a, int b){

        int c =  a;
        int d =  b; 
    }

How can i then use variable c and d in a method within the same class as the constructor because trying to use just the variables name in the method doesn't seem to work?

回答1:

In fact your code will not compile - int c = int a is not valid.

I assume that you meant: - int c = a;.

How can i then use variable c and d in a method within the same class as the constructor

You can't because you have declared them as local variables whose scope ends when the constructor ends execution.

You should declare them as instance variables.

public class MyClass {
    int c;
    int d;

    public MyClass(int a, int b){

        this.c = a;
        this.d = b; 
    }

    public void print() {
        System.out.println(c + " : " + d);
    }
}

回答2:

You need to declare the variables as class members, outside the constructor. In other words, declare c and d outside of the constructor like so:

int c;
int d;

public Constructor (int a, int b) {

        c = a;
        d = b; 
}