Java Type Promotion的源代码在哪里以及如何调试

Question

我基本上是想调试下面的Type Promotion代码来理解为x创建的临时double变量。我怎样才能做到这一点？

public class TypePromotion {

public static void main(String args[]){

    int x = 10;

    double y = 20.0;

    double z = x + y;

    System.out.println("value of Z is :: "+z); // outputs 30.0

    System.out.println("value of X is :: "+x); // outputs 10

}}