Java, "pointer" equality and string comparison

Question

I've C code that use a lot of commands identified by static string constants.

static char* KCmdA = "commandA"
static char* KCmdB = "commandB"
static char* KCmdC = "commandC"

In C I can compare two strings with strcmp(A, B) for example but as I only refer those command via their static string identifier it's faster to only check for pointer inequality since I know my unknowCMD can only be a pointer to one of my static strings.

switch(unknowCMD)
{
    case KCmdA:
    ...
    case KCmdB:
    ...
}

I guess in Java the equivalent to strcmp would be the method equals:

unknowCMD.equals(KCmdA)

Is there an equivalent of the pointer equality in Java ? I know Java uses only references. Is it possible to use those references for equality test without actually comparing the strings ?

Sorry if this is obvious I've check the doc but did not find any definitive answer.

score 6 · Answer 1 · answered Jul 11 '12 at 10:24

6

if you compare equality of string refrences Use ==

if(str1==str2){

}

answered Jul 11 '12 at 10:24

Samir Mangroliya

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Simon Nickerson · Answer 2 · 2012-07-11T10:31:04.297

4

You can use ==, but it's dangerous and brittle.

Note that for Strings, the first thing equals() does is test equality of the references, so you're not buying much by doing this.

edited Jul 11 '12 at 10:31

answered Jul 11 '12 at 10:24

Simon Nickerson

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wow that was a fast answer. OK so equals does not actually compare the string content that's good to now. That actually make me though of a related problem. How can I use a switch statement for comparing strings ? – CodeFlakes Jul 11 '12 at 10:26
2

You need Java SE 7 for that. See http://stackoverflow.com/questions/338206/switch-statement-with-strings-in-java – mmalmeida Jul 11 '12 at 10:29
What ?! it's only a recent feature ? I'm developing for Android so I won't be able to use it. Anyway thanks a lot to both of you. – CodeFlakes Jul 11 '12 at 10:32

score 3 · Accepted Answer · answered Jul 11 '12 at 10:31

3

I think that the way you are using static strings here it would be better to use Enums. You can compare them by using .equals and ==. You can use enums in switch case too.

answered Jul 11 '12 at 10:31

Jurgen Goris

66
1

Indeed. I actually did not use them because I read somewhere that it was not recommended on Android. But it would actually probably be the best approach for my problem. I'll be able to use a switch statement with enums. – CodeFlakes Jul 11 '12 at 10:35

Java, "pointer" equality and string comparison

3 Answers3