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Andreas Koch
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 Posted: Tue Jun 20, 2006 1:51 am Post subject: Porting code that uses in/out string parameters |
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Hi all,
as a java beginner who has googled a bit on the pass
by value/reference and immutable issue with java
paraemters, i wonder how to implement (or most
conveniently replace) following function:
function cuttoken(in/out fullstring:string;separator:string):string;
this function takes a string containing a separated list,
like "one;two;three", returns the part until the first separator,
and removes that parameter from the passed string. So
String test = "one;two;three"
System.out.println(cuttoken(test,";"));
System.out.println(cuttoken(test,";"));
System.out.println(cuttoken(test,";"));
would print
one
two
three
How to do this in java? Or do i have to split this up to
two calls each (part=getpart, remaining=removepart) ?
thanks,
Andreas |
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Oliver Wong
Guest
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| Posted: Tue Jun 20, 2006 2:00 am Post subject: Re: Porting code that uses in/out string parameters |
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"Andreas Koch" <nospam (AT) kochandreas (DOT) com> wrote in message
news:e772fm$467$01$1 (AT) news (DOT) t-online.com...
| Quote: | Hi all,
as a java beginner who has googled a bit on the pass
by value/reference and immutable issue with java
paraemters, i wonder how to implement (or most
conveniently replace) following function:
function cuttoken(in/out fullstring:string;separator:string):string;
this function takes a string containing a separated list,
like "one;two;three", returns the part until the first separator,
and removes that parameter from the passed string. So
String test = "one;two;three"
System.out.println(cuttoken(test,";"));
System.out.println(cuttoken(test,";"));
System.out.println(cuttoken(test,";"));
would print
one
two
three
How to do this in java? Or do i have to split this up to
two calls each (part=getpart, remaining=removepart) ?
|
You can use StringTokenizer:
<pseudoCode>
String input = "one;two;tree";
String seperator = ";";
StringTokenizer st = new StringTokenizer(input, seperator);
while (st.hasMoreTokens()) {
System.out.println(st.nextToken());
}
</pseudoCode>
or you can play around with regular expressions.
- Oliver |
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Patricia Shanahan
Guest
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| Posted: Tue Jun 20, 2006 6:34 pm Post subject: Re: Porting code that uses in/out string parameters |
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Andreas Koch wrote:
| Quote: | Hi all,
as a java beginner who has googled a bit on the pass
by value/reference and immutable issue with java
paraemters, i wonder how to implement (or most
conveniently replace) following function:
function cuttoken(in/out fullstring:string;separator:string):string;
this function takes a string containing a separated list,
like "one;two;three", returns the part until the first separator,
and removes that parameter from the passed string. So
String test = "one;two;three"
System.out.println(cuttoken(test,";"));
System.out.println(cuttoken(test,";"));
System.out.println(cuttoken(test,";"));
would print
one
two
three
How to do this in java? Or do i have to split this up to
two calls each (part=getpart, remaining=removepart) ?
thanks,
Andreas
|
*** DANGER! DANGER! untested code****
(I want to give examples of how it would look with several techniques)
If the separator is always the same for the whole sequence of splits, i
think the best solution is to split it using String's split.
String test = "one;two;three";
String[] testWords = test.split("/;/");
for(int i=0; i<testWords.length; i++){
System.out.println(testWords[i]);
}
If the separator can change, or you may want to stop before parsing out
all the pieces:
1. Use a StringBuffer or StringBuilder, shared between caller and callee:
StringBuffer test = new StringBuffer("one;two;three");
System.out.println(cuttoken(test,";"));
System.out.println(cuttoken(test,";"));
System.out.println(cuttoken(test,";"));
I don't like this, although it is closest to the method you are using,
because I don't like the shared data structure being modified by the callee.
2. Create a new class that remembers the string:
MyCut test = new MyCut("one;two;three");
System.out.println(test.cutToken(";");
System.out.println(test.cutToken(";");
System.out.println(test.cutToken(";");
A MyCut implementation might stash the string in a StringBuffer or
StringBuilder.
3. More awkward, but a general technique you can use when one method
returns multiple results, use an array result.
String test = "one;two;three";
String[] split;
split = cutToken(test,";");
System.out.println(split[0]);
split = cutToken(split[1],";");
System.out.println(split[0]);
split = cutToken(split[1],";");
System.out.println(split[0]);
Patricia |
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Andreas Koch
Guest
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| Posted: Tue Jun 20, 2006 10:08 pm Post subject: Re: Porting code that uses in/out string parameters |
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| Quote: | 2. Create a new class that remembers the string:
MyCut test = new MyCut("one;two;three");
System.out.println(test.cutToken(";");
System.out.println(test.cutToken(";");
System.out.println(test.cutToken(";");
A MyCut implementation might stash the string in a StringBuffer or
StringBuilder.
|
Great, that looks like a nice and clean way as the list only
needs setup, cuttoken and empty test.
Too bad i can't subclass the String class directly, but i can
live with a standalone class (using a instance String variable
for storage).
thanks,
Andreas |
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