Get constructor's parameter as a method's variable

Question

class Param implements Runnable {
int c;

public Param(int a, int b){
    c = a+b;
}

public void run(){
    // System.out.println(a); // <<<<----What I'm going to do. it's impossible. 
}

 }

public class ParamTest {
public static void main(String args[]){
    Runnable r = new ThreadParam(10,20);
    new Thread(r).start();  

}   
}

In above code, How can I print the value of "a"? My goal is, when I call Runnable r = new ThreadParam(10,20) in main method, I want to print value of "a" --> 10 . Is this impossible? If I declare int a into run() method, the result of "a" is '0'. I want to the result "10". How can I do that?

Change your design and add an instance variable that stores the value of `a`. — Sotirios Delimanolis, Dec 17 '13 at 19:40
Possible duplicate:- http://stackoverflow.com/questions/20640896/passing-parameters-to-java-thread — Rahul Tripathi, Dec 17 '13 at 19:41
@RahulTripathi That was my question. But I stucked another problem : this question. Please consider it, Thank you. — ton1, Dec 17 '13 at 19:45

score 3 · Answer 1 · answered Dec 17 '13 at 19:40

3

Local variables and parameters only exist inside the function that declared them.
You need to store it in a field in the class, just like you stored c.

answered Dec 17 '13 at 19:40

SLaks

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Declare `int a` into class? or method? then its result is 0. How can I print 10? – ton1 Dec 17 '13 at 19:51
@user3100921: You need to declare it in the class, then assign it in the constructor. `int a` in the class and `int a` in the constructor are two different and unrelated variables. – SLaks Dec 17 '13 at 19:52

score 2 · Accepted Answer · answered Dec 17 '13 at 19:41

2

Create another instance variable to hold the a value:

int a;

and in your constructor, copy it down:

this.a = a;

Then you can access it in another method.

answered Dec 17 '13 at 19:41

rgettman

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Where is proper position of `int a`? I want to print value of "a" not 0, but 10. is this impossible? – ton1 Dec 17 '13 at 19:53
Declare it next to your other instance variable, `c`. – rgettman Dec 17 '13 at 19:56

Get constructor's parameter as a method's variable

2 Answers2