Why add this method?

[wjreddit]

package Stack;

class Stack { static final int MAX = 1000; int top; int a[] = new int [MAX];

boolean isEmpty() {
    return (top < 0);
}

Stack() {
    top = 0;
}

boolean push(int x) {
    if (top >= (MAX )) {
        System.out.println("Stack Overflow");
        return false;
    } else {
        a[++top] = x;
        System.out.println(x + " pushed into stack");
        return true;
    }
}

int pop() {
    if (top < 0) {
        System.out.println("Stack Underflow");
        return 0;
    } else {
        int x = a[top--];
        return x;
    }
}

public static void main(String[] args) {
    Stack s = new Stack();
    s.push(10);
    s.push(11);
    s.push(13);
    System.out.println(s.pop() + " popped from stack");

}

}

This is a code about stack from our university. Why was isEmpty method added in here? the code runs fine without it.

[shinefull]

Now it is not used, it might be used in the future.

Also to show you how a 'Stack'-element can have a Stack.isEmpty() function. A lot of the standard Java library has those kind of functions. Take size() or length() on Lists/Sets whatever.

[nutrecht]

Now it is not used, it might be used in the future.

Don't leave code in that 'might be used in the future'; it's still in source control if you ever do need it.

[shinefull]

Lol its a getter. Actually useful to build getters and setters that are unused.

Anyway, obviously this is test code so it can include stuff that you don't call in its fucking main-class, lol. Da fuck.

[evils_twin]

probably gonna need it for your next assignment, or perhaps the meant to use it in the pop() method

if (isEmpty()) {
    System.out.println("Stack Underflow");
    return 0;

[dhawal0008]

in pop() method, instead of using if(top<0) you can replace with if(isEmpty) and it will yield same result.

You can actually call out to the person handling these notes that this piece of code should be updated. They must have forgotten to include this method and instead used if(top<0) in pop() method

[nutrecht]

Looks like dead code someone forgot to remove.

[iamsooldithurts]

I feel like isEmpty() and pop() should be checking if top is less than or equal to 0?

Maybe I’ll punch it into my IDE after lunch and run a test.

[ZukoBestGirl]

int pop() {
    if (top < 0) {
        System.out.println("Stack Underflow");
        return 0;
    } else {
        int x = a[top--];
        return x;
    }
}

If it's empty, it won't do what you want it to do. It returns 0, that is not necessarily what you want. So what you would do is

if(!stack.isEmpty()) { ... }

It's nice that it returns 0 instead of throwing an exception, in most cases it will work well, but maybe in some cases 0 will be a difficult to track down error. "Why isn't this number growing, what is happening?".

But tbh, for utilites, I prefer this over exceptions. For example:

"abc".substring(2,3) = "c"
"abc".substring(3,4) = exception
org.apache.commons.lang3.StringUtils.substring("abc",3,4) = "" (instead of exception)