3/25 Warmup Hack (Stacks & Heaps) - Aiden Huynh, P1

[aidenhuynh]

camelCase title "StackHeapTest"

New file within SpringPortfolio/hacks

StackHeapTest Object

Note: To run the file, I just pressed 'run' in the top-right, then clicked on a random parent class (I think I used Alphabet?)

package com.nighthawk.hacks;

public class StackHeapTest {
    public int n = 5; // primitive data type on the heap

    public static void changeInt(int nValue, int nRefN, StackHeapTest nRef, Integer number) {
        // Before changes
        System.out.println("\n\n\nBEFORE CHANGES: (Inside Object):");
        System.out.println("\nn:\nvalue = " + nValue + "\n" + "hash = " + System.identityHashCode(nValue));
        System.out.println("\nnRefN:\nvalue = " + nRefN + "\n" + "hash = " + System.identityHashCode(nRefN));
        System.out.println("\nInteger:\nvalue = " + number + "\n" + "hash = " + System.identityHashCode(number));

        // Add 10 to all parameters
        nValue += 10;
        nRefN += 10;
        nRef.n += 10;
        number += 10;

        // After changes
        System.out.println("\n\n\nAFTER CHANGES: (Inside Object)");
        System.out.println("\nn:\nvalue = " + nValue + "\n" + "hash = " + System.identityHashCode(nValue)); // Changes
        System.out.println("\nnRefN:\nvalue = " + nRefN + "\n" + "hash = " + System.identityHashCode(nRefN)); // Changes
        System.out.println("\nInteger:\nvalue = " + number + "\n" + "hash = " + System.identityHashCode(number)); // Changes
    }

    public static void main(String[] args) {
        // primitive data types on the stack
        int n = 5; 
        int nRefN = 5;
        Integer number = 5;

        StackHeapTest nRef = new StackHeapTest();

        // Initial Values (Stack)
        System.out.println("\nINITIAL VALUES: (Outside Object)");
        System.out.println("\nn:\nvalue = " + n + "\n" + "hash = " + System.identityHashCode(n));
        System.out.println("\nnRefN:\nvalue = " + nRefN + "\n" + "hash = " + System.identityHashCode(nRefN));
        System.out.println("\nnRef.n:\nvalue = " + nRef.n + "\n" + "hash = " + System.identityHashCode(nRef.n));
        System.out.println("\nInteger:\nvalue = " + number + "\n" + "hash = " + System.identityHashCode(number));

        // Run method
        nRef.changeInt(n, nRefN, nRef, number);

        // Final Values (Stack)
        System.out.println("\n\n\nFINAL VALUES: (Outside Object)");
        System.out.println("\nn:\nvalue = " + n + "\n" + "hash = " + System.identityHashCode(n)); // No change
        System.out.println("\nnRefN:\nvalue = " + nRefN + "\n" + "hash = " + System.identityHashCode(nRefN)); // No change
        System.out.println("\nnRef.n:\nvalue = " + nRef.n + "\n" + "hash = " + System.identityHashCode(nRef.n)); // Change
        System.out.println("\nInteger:\nvalue = " + number + "\n" + "hash = " + System.identityHashCode(number)); // No change
    }
}

Output

Mr. Mortensen recommended one line per value + hash, but this looks nicer on an issue (i.e. n: value = 5, hash = 245565335)

INITIAL VALUES: (Outside Object)

n: value = 5 hash = 245565335

nRefN: value = 5 hash = 245565335

nRef.n: value = 5 hash = 245565335

Integer: value = 5 hash = 245565335

BEFORE CHANGES: (Inside Object):

n: value = 5 hash = 245565335

nRefN: value = 5 hash = 245565335

Integer: value = 5 hash = 245565335

AFTER CHANGES: (Inside Object)

n: value = 15 hash = 2065530879

nRefN: value = 15 hash = 2065530879

Integer: value = 15 hash = 2065530879

FINAL VALUES: (Outside Object)

n: value = 5 hash = 245565335

nRefN: value = 5 hash = 245565335

nRef.n: value = 15 hash = 2065530879

Integer: value = 5 hash = 245565335

## Reflection

This was a helpful exercise for better understanding and visually seeing how stacks and heaps work. You can see that within the object, each changed value is stored in the stack and thus can only be referenced within the method/object. In the main method though, each value is stored in the heap and thus does not output the values changed within the object, except for ``nRef.n`` which *is* part of the object, thus accessing the stack.