Are the or pipes not working?

Question

For my very first Java project I'm trying to make a simple text-based game. It seems like the or pipes do not work and when I try to enter something in after it doesn't work; I have to restart it.

    public void GameStart() {
    String playerName = "Player";
    String Command = "Choice";
        System.out.println("Type Start to start game!");
    if(in.nextLine().equals("Start") || in.nextLine().equals("start")) {
        Help();
        print("Type Begin to start game :D");
        if(in.nextLine().equals("Begin") || in.nextLine().equals("begin")) {
            System.out.println("Who are you?");

Start and Begin works, but having the first letter lowercase like I used || for doesn't. When I use those I have to restart it because I can't type anything, but I clearly have or pipes that says to use either one. Does anyone have any idea what is causing this?

Answer 1

in.nextLine().equals("Start") || in.nextLine().equals("start")

This will be executed from left to right, so first in.nextLine().equals("Start") is executed.

Let's say you input "start". Left side returns false. Evaluation of the whole expression continues. The right side is executed, in.nextLine().equals("start"). So, it reads another line, waits for your another input. This is not what you want.

To fix this (this is also a general rule): do not change the state in the if condition. In other words: expression in the condition should have no side effects.

You can assign the result of the method which is changing the state, in.nextLine(), to a reference:

String line = in.nextLine();
if (line.equals("Start") || line.equals("start"))

You can also write the condition like:

if (line.equalsIgnoreCase("start"))

or

if (line.toLowerCase().equals("start"))

Now, any case combination is alright, even "START".

Last but not least: these || are not called pipes. If you use word "pipe" in programming context, a lot of people will think about Unix pipes, | symbol in the command line.

In Java || is "logical or operator", "logical or". To distinguish with "binary or", |, which is very different.

Answer 2

String str = in.nextLine();
str.equalsIgnoreCase("Start");

It will check both the lower and upper cases. You don't need to call equals() method twice, so it will optimize your code and readability.

I hope this will solve your issue.