array confusion


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  1. #1
    Join Date
    Sep 2006
    Posts
    23

    array confusion

    Question about two peices of code
    1.
    Code:
    {
    		int i=0;
    		int j=0;
    		int total=0;
    		while(Character.isWhitespace(lines[i].charAt(j)))
    		{
    			total++;
    			i++;
    			j++;
    		}
    		return total;
    this should show the number of characters in an already loadaded file but it doesnt

    2How do you take a file with blank lines in it and crunch it up for example
    this is

    a file

    now
    should turn into

    this
    is
    a file
    now

  2. #2
    Join Date
    Sep 2006
    Posts
    68
    I)

    Code:
    int total=0;
    for (int lineIndex=0; lineIndex < lines.length; lineIndex++) {
    	String str = lines[lineIndex];	
    	if ( int j = 0; j < str.length; j++ ) {
    		if (!Character.isWhitespace(str.charAt(j))) { // if you do not want to calculate whitespaces 
    			total++;
    		}
    	}
    }

    II)
    Code:
    BufferedReader br = new BufferedReader(XXX); // XXX - your input stream e.g. FileInputStream
     String line;
     while ((line = br.readLine()) != null) {
          if (line.trim().size()str == 0) {
          	continue; // skip empty string
          }
          ....      
     }

  3. #3
    Join Date
    Sep 2006
    Posts
    23
    Can you show it without continue and also your the first one doesnt work
    Last edited by torrinment; 10-09-2006 at 05:21 PM.

  4. #4
    Join Date
    Sep 2006
    Posts
    68

    Thumbs down

    Code:
    for (int lineIndex=0; lineIndex < lines.length; lineIndex++) {
    	 String line = lines[lineIndex];	
    	 if (!line.trim().size() == 0) {
            	System.out.println(line);
    ...
    
       }
    }

  5. #5
    Join Date
    Sep 2006
    Posts
    23
    the character count one doesnt work either

    Code:
    {
    		int i=0;
    		int j=0;
    		int total=0;
    		while(Character.isWhitespace(lines[i].charAt(j)))
    		{
    			total++;
    			i++;
    			j++;
    		}
    		return total;
    Last edited by torrinment; 10-09-2006 at 05:34 PM.

  6. #6
    Join Date
    Sep 2006
    Posts
    68
    The character count:

    Code:
     int total = 0;
            String[] lines = new String[] {
                    "abcdef", "123", "qwer ty" // 15 chars + 1 space
            };
            for (int lineIndex=0; lineIndex < lines.length; lineIndex++) {
                String str = lines[lineIndex];
                for (int j = 0; j < str.length(); j++ ) {
                    if (!Character.isWhitespace(str.charAt(j))) { // if you do not want to calculate whitespaces
                        total++;
                    }
                }
            }
            System.out.println(total);

  7. #7
    Join Date
    Sep 2006
    Posts
    23
    do you know what a nullpointer exception is

  8. #8
    Join Date
    Sep 2006
    Posts
    68
    Quote Originally Posted by torrinment
    do you know what a nullpointer exception is
    Yes I know. It happens when you try to do with something that don't exsists.

    For example:
    String s = null;
    s.trim(); // throws NullPointerException

  9. #9
    Join Date
    Sep 2006
    Posts
    68
    Second example:

    Code:
    String[] lines = new String[] {
                    "this", "   ", "is", "a" , " ",  "test" };
            for (int lineIndex=0; lineIndex < lines.length; lineIndex++) {
    	    String line = lines[lineIndex];
    	    if (!(line.trim().length() == 0)) {
            	System.out.println(line);
                }
            }

    PS: I often post a programs which I don't check. I think small errors like misprints you can correct yourself.

  10. #10
    Join Date
    Sep 2006
    Posts
    23
    that works but gives me a nullpointerexception how do i fix this like it does what it supposed to but then i get that exceptio n

  11. #11
    Join Date
    Sep 2006
    Posts
    68
    Quote Originally Posted by torrinment
    that works but gives me a nullpointerexception how do i fix this like it does what it supposed to but then i get that exceptio n
    It's difficult to answer because I don't know your code. Please attach a whole your application or am exception stack trace.

    BTW: check that you nowhere set empty values to variables.

  12. #12
    Join Date
    Sep 2006
    Posts
    23
    no im just talkin about both the character count you showed me and the eliminate vspace
    Code:
    public static int charCount(String[]lines)
    	{
    		 int total = 0;
    	       for (int i=0; i < lines.length; i++) 
    	       {
    	    	   for (int j = 0; j < lines[i].length(); j++ ) 
    	       {
    	    	   if (!Character.isWhitespace(lines[i].charAt(j))) {
    	    		   total++;
    	                }
    	            }
    	        }
    	        System.out.println(total);
    		return total;
    	}
    and
    Code:
    public static void EliminateVSpace(String[]lines)
    	{
            for (int lineIndex=0; lineIndex < lines.length; lineIndex++) {
    	    String line = lines[lineIndex];
    	    if (!(line.trim().length() == 0)) {
            	System.out.println(line);
                }
            }
    }

  13. #13
    Join Date
    Sep 2006
    Posts
    68
    I understand. The exception happens because you pass lines with empty values.
    For example
    if you pass such array:
    String[] lines = new String[] {"this", " ", "is", null, "a", "test" };
    it will produce an exception.

  14. #14
    Join Date
    Sep 2006
    Posts
    23
    so i fix it by...

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