How to extract strings

Question

I'm new to Java programming. I want to write simple Java network protocol. I want to send this string to remote Java host, for example:

230 computer delete reboot exit

The problem that I cannot resolve is how I can extract the strings one by one and put it into array? And the biggest mystery to me is how I do this if I have strings with different length? Thank you for your help!

PS: Can I send directly entire array not just simple strings?

PS 2: What if I have Java server and C client? As far as know only strings can be used to exchange data between both sides?

I can't speak about sending to a remote Java host, but one can convert a string to an array with the `.split()` function. `"230 computer delete reboot exit".split("\\s+")` will split your string by whitespace into an array of 5 elements. — Ina, Jun 13 '12 at 14:16
you don't know it yet, but this isn't your *biggest* problem ... — , Jun 13 '12 at 14:17
You have to decide how you want to serialize your data, if you want to send something more complicated like arrays. Look at http://en.wikipedia.org/wiki/Comparison_of_data_serialization_formats for some alternatives. — Christoffer Hammarström, Jun 13 '12 at 14:25

score 4 · Answer 1 · edited May 23 '17 at 11:58

4

String input = "230 computer delete reboot exit";
String s[] = input.split("\\s+");

// now s[0] = 230 s[1] = computer

Read more on String.split().

And the regex used here \\s+ is equal to any whitespace. Read this for further information.

edited May 23 '17 at 11:58

Community

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answered Jun 13 '12 at 14:15

Kazekage Gaara

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dacwe · Accepted Answer · 2012-06-13T14:22:14.847

4

You can either:

Split the strings using String.split method

String text = "230 computer delete reboot exit";
String[] split = text.split("\\s");

Using a Pattern and a Matcher

String text = "230 computer delete reboot exit";
Pattern p = Pattern.compile("(.*)\\s+(.*)\\s+(.*)\\s+(.*)\\s+(.*)");
Matcher m = p.matcher(text);
if (m.matches()) {
    String first = m.group(1);
    String second = m.group(2);
    ....

Using a Scanner class

Scanner s = new Scanner(text);
int firstNumber = s.nextInt(); // 230
String secondText = s.next(); // computer
....

The second and the third choice could be superior if read stuff from a stream.

Or some other method... :)

edited Jun 13 '12 at 14:22

answered Jun 13 '12 at 14:16

dacwe

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One more question: If I want to connect Java server and C client what is the most elective way to exchange data? Strings? – user1285928 Jun 13 '12 at 14:23
Define a binary or textual protocol. In your case you can start with strings just like you defined in your question. – dacwe Jun 13 '12 at 14:24

score 3 · Answer 3 · answered Jun 13 '12 at 14:18

You can send directly an array by using serialization through ObectInputStream and ObjectOutputStream.

But I suggest you to use your own classes to encapsulate messages. Eg

class NetworkMessage {
  int code;
  String param1;
  String param2;
  ..
}

So that it's more object oriented and structured. Sending just strings is not a good design, especially if the protocol grows in complexity.

Regarding splitting the string just use String.split(String regex) method but it's not a good solution.

How to extract strings

3 Answers3