using a variable in constructor in a method outside of constructor

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);
    }
}