LeJOS lacks (?) String.split()

[MaR1oC]

Hello,

I've started a LeJOS PC Project in my computer (using Eclipse IDE LeJOS NXJ Plugin) but I am facing a problem:

There is no split() method in the String class (java.lang.String). I have double checked the API and I didn't find anything referring to String.split()

How can I implement this method in my LEJOS NXJ Runtime??

Thanks in advance!

[skoehler]

Well, you do know that String.split() uses regular expressions? So in order to implement String.split(), you first need to implement regular expressions.
Well, and using String.split() is really not the best thing to do, performance wise. Even if it would exist on the NXT.

Be a programmer, and split the string yourself. It's really not that hard. I guess, you're just going to split by comma or spaces or whatever anyways.

[MaR1oC]

I am develioping a GCode Controller for the NXT Brick

[skoehler]

I am develioping a GCode Controller for the NXT Brick

And what would that be? And what should it tell me about why you want to use String.split? Do you actually need support for regular expressions?

[gloomyandy]

GCode is a CNC control language.

[skoehler]

GCode is a CNC control language.

Googled a bit, found some GCode sample code. Couldn't think of any task that couldn't be easily done with indexOf()+substring() instead of split().

[MaR1oC]

GCode is a CNC control language.

Googled a bit, found some GCode sample code. Couldn't think of any task that couldn't be easily done with indexOf()+substring() instead of split().

I agree with you. It would take a long time :/

@skoelher Check out my project http://code.google.com/p/lego-mindstorms-3d-printing-machine/

UPDATE: I have been thinking of a solution like this:

Code: Select all

   private static String[] split(String s, String S) {
      String[] str = {};
      try {
         for (int i = 0; i<=S.length(); i++) {
            int c = S.indexOf(s) - 1;
            str[i] = S.substring(0,c);
            S = S.substring(c+1);
         }
         return str;
      } catch (Exception e) {
         return null;
      }
   }

[skoehler]

@skoelher Check out my project http://code.google.com/p/lego-mindstorms-3d-printing-machine/

Yeah, I found your parser. Well, I don't know where to start. When I see that you compare two String object with ==, and when I see that you do these comparisons for Strings of one letter only - well, I just have to tell you that you think about using char more often. And furthermore, you probably want to learn about why comparing Strings with == does sometimes work - but not always - and why there is an equals() method to use instead.

Also, you're using SVN the wrong way. I see all the Eclipse project files in the root of the SVN, and trunk, branches, and tags seems to be subfolders of your project. You should create a subfolder for your project inside trunk. Move everything to that subfolder.

[skoehler]

Code: Select all

   private static String[] split(String s, String S) {
      String[] str = {};
      try {
         for (int i = 0; i<=S.length(); i++) {
            int c = S.indexOf(s) - 1;
            str[i] = S.substring(0,c);
            S = S.substring(c+1);
         }
         return str;
      } catch (Exception e) {
         return null;
      }
   }

The line S = S.substring(c+1); kills the performance. Well, at least for large strings which contains very the substring s very often. Also, arrays in Java do not grow dynamically. Use this:

Code: Select all

   private static String[] split(String s, String S) {
      ArrayList<String> list = new ArrayList<String>();
      int start = 0;
      while (start < S.length()) {
         int end = S.indexOf(s);
         if (end < 0)
            break;
         
         list.add(S.substring(start, end));
         start = end + s.length();
      }
      if (start < S.length())
         list.add(S.substring(start));
      return list.toArray(new String[list.size()]);
   }

The code comes without warrenty. I hope, I have catched all corner cases.

[MaR1oC]

Code: Select all

   private static String[] split(String s, String S) {
      String[] str = {};
      try {
         for (int i = 0; i<=S.length(); i++) {
            int c = S.indexOf(s) - 1;
            str[i] = S.substring(0,c);
            S = S.substring(c+1);
         }
         return str;
      } catch (Exception e) {
         return null;
      }
   }

The line S = S.substring(c+1); kills the performance. Well, at least for large strings which contains very the substring s very often. Also, arrays in Java do not grow dynamically. Use this:

Code: Select all

   private static String[] split(String s, String S) {
      ArrayList<String> list = new ArrayList<String>();
      int start = 0;
      while (start < S.length()) {
         int end = S.indexOf(s);
         if (end < 0)
            break;
         
         list.add(S.substring(start, end));
         start = end + s.length();
      }
      if (start < S.length())
         list.add(S.substring(start));
      return list.toArray(new String[list.size()]);
   }

The code comes without warrenty. I hope, I have catched all corner cases.

Your method returns that "the s String is out of range: -1 ".

Moreover, I really appreciate your help (all of you guys & perhaps girls) and it seems that it is a good way to learn by my faults

[skoehler]

How about this one?

Code: Select all

       private static String[] split(String s, String S) {
          ArrayList<String> list = new ArrayList<String>();
          int start = 0;
          while (start < S.length()) {
             int end = S.indexOf(s, start);
             if (end < 0)
                break;
             
             list.add(S.substring(start, end));
             start = end + s.length();
          }
          if (start < S.length())
             list.add(S.substring(start));
          return list.toArray(new String[list.size()]);
       }

[MaR1oC]

How about this one?

Code: Select all

       private static String[] split(String s, String S) {
          ArrayList<String> list = new ArrayList<String>();
          int start = 0;
          while (start < S.length()) {
             int end = S.indexOf(s, start);
             if (end < 0)
                break;
             
             list.add(S.substring(start, end));
             start = end + s.length();
          }
          if (start < S.length())
             list.add(S.substring(start));
          return list.toArray(new String[list.size()]);
       }

Worked well for me ! Thanks!