Java: Validating a string

Question

So I am working on a project in java and I have just a quick question.

I have a method that is receiving a string and I want to strip out the spaces and check that is is not empty. So far I have the below in place however it doesn't seem to be working properly.

public static Boolean isValid(String s) {
    s.replace(" ", "");
    if (s == ""){
        return false;
    }
    else {
        return true;
    }
}

Any help would be appreciated :) Ta

instead of `s == ""` use `"".equals(s)` – EpicPandaForce Nov 05 '14 at 11:16 — EpicPandaForce, Nov 05 '14 at 11:16

score 6 · Answer 1 · edited Nov 05 '14 at 12:01

6

You can try with this:

public static Boolean isValid(String s) {
    return (!s.trim().isEmpty());
}

edited Nov 05 '14 at 12:01

vefthym

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answered Nov 05 '14 at 11:16

jjlema

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Actually, this does only remove the leading and trailing spaces. `s.replace()` will also replace the spaces in the middle of the string. – Magnilex Nov 05 '14 at 11:25
@Magnilex if there is a white space in the middle of the string, then there are non-whitespace chars in the string... the result is the same! – vefthym Nov 05 '14 at 11:27
1

Yes, of course. You are correct. +1 for the most elegant solution. – Magnilex Nov 05 '14 at 11:37
I agree that this is the most elegant solution and the one that should be accepted. – vefthym Nov 05 '14 at 11:39

score 2 · Accepted Answer · edited Nov 05 '14 at 11:19

2

First you have forgot the assignment for s.replace(" ",""). Store that in a variable, e.g.

x = s.replace(" ","");

For string comparison use .equals() method instead of ==

edited Nov 05 '14 at 11:19

Graham Borland

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answered Nov 05 '14 at 11:19

Harry

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score 1 · Answer 3 · answered Nov 05 '14 at 11:17

You can use the following code as well :

newString=myString.replaceAll("\\s+",""); This removes one or more spaces in between Strings as well as leading and trailing whitespaces

Use : myString.trim() to remove only leading and trailing whitespaces

and then newString.isEmpty()

You should use .equals() to compare Strings

score 1 · Answer 4 · answered Nov 05 '14 at 11:17

1

When you're comparing strings, use .equals(). Its only in artihmetic expressions you use the == sign

TO check whether your string is empty use the .isEmpty() function

answered Nov 05 '14 at 11:17

Prasanth Louis

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Michael · Answer 5 · 2014-11-05T11:27:01.833

1

You forgot the assignment:

s = s.replace(" ", "");

EDIT: for the comments stating that == is not working. I wanted to say that it does work for Java 7

edited Nov 05 '14 at 11:27

answered Nov 05 '14 at 11:17

Michael

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Sagar Pudi · Answer 6 · 2014-11-05T11:39:46.620

1

replaceAll() method supports regular expressions as well as isEmpty() is already there in String class so we can reuse it and is safer to use here.

simply use like this:

public static Boolean isValid(String s) {
    s = s.replaceAll("\\s", "");
    if (s.isEmpty()) {
        return false;
    } 
    else {
        return true;
    }
}

edited Nov 05 '14 at 11:39

answered Nov 05 '14 at 11:30

Sagar Pudi

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score 0 · Answer 7 · edited May 23 '17 at 10:25

0

Difference between equals and == incase of String comparison is well explained in the thread

value of s.replace() should be assigned to itself or some other variable.

edited May 23 '17 at 10:25

Community

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answered Nov 05 '14 at 11:31

Logan

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Java: Validating a string

7 Answers7