为什么我不能在Java中删除空格？

Question

I'm desperately trying to remove white spaces from a String (that late i want to be able to convert into an int) but i can't seem to get it all right.

String input;
if(GamePlay.GameStart == true){
    input = Terminal.askString("Welcome to MASTERMIND! \n Please Give in Your Game Attributes \n");
            input.replaceAll("\\s","");
}else
    input = Terminal.askString(""); 
if (input.equals("Quit") || input.equals("quit")){
    Quit();

}
else if(GamePlay.GameStart == true){

    System.out.println(input); .......(code follows)

Can you please tell me,what it is that i'm doing wrong? PS:I've tried \\W" and \\S" too

Answer 1

replace

input.replaceAll("\\s","");

with

input = input.replaceAll("\\s","");

It will work, because strings are immutable, so replaceAll() won't change your string object, it will return a new one. So you assign your variable input to the string returned by input.replaceAll("\\\\s","");

Also, you should try to follow the Java naming conventions, and have your fields and variables start with a lowercase letters.

And, you can also replace

if(GamePlay.GameStart == true) {

with

if(GamePlay.GameStart) {

because in your version you compare the value of GamePlay.GameStart with true , and only execute the if block if that evaluation is true , whereas in my version, the ìf block is executed if GamePlay.GameStart is true (although the compiler probably optimizes it away anyway).

On another note, you can also replace

if (input.equals("Quit") || input.equals("quit")){

with

if (input.equalsIgnoreCase("Quit")) {

because, well I think it's obvious.

Answer 2

Strings are immutable. You need to assign your result of the newly created String returned by replaceAll :

input = input.replaceAll("\\s","");

Answer 3

input.replaceAll("\\\\s",""); returns a string with the spaces removed. But if you don't keep a reference to it you won't be able to see the result. You probably meant:

input = input.replaceAll("\\s","");

Answer 4

This is a very common mistake for beginners.

As others have mentioned, you need to know that replaceAll returns a new string and doesn't change the current one, since strings are immutable in Java.

So use:

input=input.replaceAll("\\s","");

If you wish, you can have assistant plugins to help you with such bugs, such as findBugs and codePro .