Heap Stack Diagram from Code

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Hey I am in the middle of Java and I am having trouble drawing heap stack diagrams from code. I have two that I really need help with.

First code:

public class HEAPSTACK extends ConsoleProgram{
public void run(){
Integer n1=1;
Integer n2=20;
int computation=meth(n1,n2);
println("computation:"+computation);

Draw the heap-stack diagram when println has been called but before it runs}

private int meth(int n2, int n1){
Draw the heap-stack diagram when execution reaches this point return n2-n1;}}

Second Code:

public clas HEAPSTACK extends ConsoleProgram(
public void run(){
Rational a=new Rational(1,7);
Rational b=new Rational(3,7);
Rational c=a;
Rational d=meth1(a,b);
Draw the heap-stack diagram when execution reaches here}

private Rational meth1(Rational x, Rational y){
Rational z=x.add(y);
return meth2(z);}
private Rational meth2(Rational p){
Rational a=new Rational (0,7);
Draw the heap-stack diagram for when execution reaches here
return (a.subtract(p));
}}