Java - If statement not working (comparing strings)

Question

When I grab the IP Address from my open socket, as someone has sent me a stream, I noticed that the IP has a forward-slash.

I just plan to simply omit it. But first I want to validate the first character in the string is the forward-slash:

String dataSource = data.getAddress().toString();

if(dataSource.substring(0,1) == "/"){
    System.out.println("trailing forward slash, delete it ");  
    dataSource = dataSource.substring(1);
}

This IF statement isn't being detected.

Anyone see what I'm doing wrong?

Use .equals to compare the content. == always compare by reference. — nhahtdh
– nhahtdh, Commented Dec 19, 2012 at 4:15
@nhahtdh That is true. However, he is obviously a beginner(no offense) and there is no reason to downrate him for this. I counter with an upvote. — FrostyFire
– FrostyFire, Commented Dec 19, 2012 at 4:16
legitamate question, ameture yes, but not a silly question and was worded correctly. — Sean F
– Sean F, Commented Dec 19, 2012 at 4:18
@Sean F yeah, he is trying. I have been in his shoes before with stuff like this. — FrostyFire
– FrostyFire, Commented Dec 19, 2012 at 4:19
Take a look at comparing references vs primitive data types (Srinivas B has a good point). After you get that, take a look at string object pooling and interning just to confuse yourself a little bit! ;) — Marsellus Wallace
– Marsellus Wallace, Commented Dec 19, 2012 at 4:36

Abubakkar · Accepted Answer · 2012-12-19 04:15:21Z

2

For string comparisons use equals method, as it is more reliable than using == operator (it compares the content while == comnpares the references ) :

Try using equals method :

if(dataSource.substring(0,1).equals("/")){

answered Dec 19, 2012 at 4:15

Abubakkar

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Comments

Nidhish Krishnan · Accepted Answer · 2012-12-19 04:16:13Z

2

please use .equals

if("/".equals(dataSource.substring(0,1))){
    System.out.println("trailing forward slash, delete it ");  
    dataSource = dataSource.substring(1);
}

instead of ==

answered Dec 19, 2012 at 4:16

Nidhish Krishnan

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Comments

Srinivas B · Accepted Answer · 2012-12-19 04:17:35Z

2

If you want to test only, the first character , you can try the method,

dataSource.charAt(0)=='/'

answered Dec 19, 2012 at 4:17

Srinivas B

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Comments

Sean F · Accepted Answer · 2012-12-19 22:11:35Z

1

you should use .equals for string comparrisons so

if(dataSource.substring(0,1) == "/")

should be

if ("/".equals(dataSource.substring(0,1)))

edited Dec 19, 2012 at 22:11

answered Dec 19, 2012 at 4:15

Sean F

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Comments

Michael · Accepted Answer · 2012-12-19 04:15:09Z

0

You're comparing strings with ==, which means you're checking to see if these two strings are literally the same string reference.

Use equal() to check and see if two strings contain the same characters.

See: http://www.leepoint.net/notes-java/data/expressions/22compareobjects.html

answered Dec 19, 2012 at 4:15

Michael

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Timr · Accepted Answer · 2012-12-19 04:15:26Z

0

Use .equals(Object) or .equalsIgnoreCase(String) for comparing Strings.

answered Dec 19, 2012 at 4:15

Timr

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darcyy · Accepted Answer · 2012-12-19 04:16:34Z

0

You need to do dataSource.substring(0,1).equals("/"), which actually checks the content of the strings. == only checks whether both sides are the same object.

answered Dec 19, 2012 at 4:16

darcyy

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Comments

Asish AP · Accepted Answer · 2012-12-19 04:17:07Z

0

Try this

if (("some string to check").equals(myString)){ doSomething(); }

answered Dec 19, 2012 at 4:17

Asish AP

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Comments

Amit Deshpande · Accepted Answer · 2012-12-19 04:28:55Z

0

Always use equals when comparing values. Having said that you can just use indexOf method for your purpose

   if (dataSource.indexOf('/') == 0) {
        dataSource = dataSource.substring(1);
    }

answered Dec 19, 2012 at 4:28

Amit Deshpande

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QuokMoon · Accepted Answer · 2012-12-19 04:52:06Z

0

String dataSource = "/hell";

        if(dataSource.substring(0,1).equalsIgnoreCase("/")){
            System.out.println("trailing forward slash, delete it ");  
            dataSource = dataSource.substring(1);
        }

run this program. this is working..

answered Dec 19, 2012 at 4:52

QuokMoon

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user207421 · Accepted Answer · 2012-12-19 09:31:20Z

0

Why use a String? You're just creating this problem for yourself. Use the datatype provided:

InetAddress dataSource = data.getInetAddress();

or

SocketAddress dataSource = data.getRemoteSocketAddress();

Then you have a semantically-aware .equals() method in both cases.

edited Dec 19, 2012 at 9:31

answered Dec 19, 2012 at 7:09

user207421

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