int peek() {
    if(isEmpty()) {
        System.out.println("Stack underflow peek can't be done");
        return Integer.MIN_VALUE;
    }
    else {
    
    return list.get(list.size()-1);
    }
}

Is there any other way to return nothing?

CodePudding user response：

You generally have several ways to signal an error back to the caller:

1. Return a dummy value that indicates an error, such as Integer.MIN_VALUE. Generally not favoured, will lead to problems if the dummy value naturally occurs in the data.
2. Return a null value. Requires the return type to be changed to a reference type such as Integer. Also out of fashion as nulls have various well-documented issues.
3. Change the return type to be one of the Optional types, such as OptionalInt, and return an empty value if an error occurs.
4. Throw an exception.

Your code is using option #1, which is not generally recommended, but may make sense in very specific cases (e.g. min function over a list of integers). #4 is generally the preferred option, with #3 as an alternative if you want to avoid exceptions for any reason.

CodePudding user response：

This is commonly used as indicator to caller that queue/stack is empty. The problem is return type is primitive int , so you have to return some integer, you cannot return null.

I see this in many examples because programmer assumes here that Integer.MIN_VALUE will be never valid case and nobody will push that value onto queue/stack.

Ideally I would return Integer instead of int and return null if stack is empty. We could throw exception but I will avoid it since caller will need to handle exception for every peek or top or pop. Handling null is easier than this.