CODEWITHSUNDEEP
javastringtokenizer
dwwilson66
dwwilson66

Reputation: 7066

Why can't I access the first token returned from Java's StringTokenizer?

I'm using Buffered Reader to pass individual lines of a file to Java's StringTokenizer. The file is structurd as follows: 

"2,0";"foo";"foo.doc";"12345"
"2,4";"foo";"foo.doc";"34567";"foo7";"foo7.doc";"45678";"foo6";"foo6.doc";"56789";"foo5";"foo5.doc";"67890";"foo4";"foo4.doc";"23456"   
"3,0";"foo7";"foo7.doc";"34567"
"3,0";"foo6";"foo6.doc";"45678"
"3,0";"foo5";"foo5.doc";"56789"
"3,0";"foo4";"foo4.doc";"67890"

Here's the code I'm using.

public class parse {
  public static void main(String args[]) {
    FileInputStream inputStream = new FileInputStream("whidata0.txt");
    BufferedReader br = new BufferedReader(new InputStreamReader(inputStream)); 
    while((scrubbedInput=br.readLine())!=null) {
      StringTokenizer strTok = new StringTokenizer(scrubbedInput, ";", false);
      int tokens = strTok.countTokens();
      while (strTok.hasMoreTokens()) {
        tok01 = strTok.nextToken();
      }
      System.out.println("  scrubbed: " + scrubbedInput);
      System.out.println("    tokens: " + tokens);
      System.out.println("     tok01: " + tok01);
    }
  }
}

which yields this result.

scrubbed: "2,0";"foo";"foo.doc";"12345" 
  tokens: 4
   tok01: 12345  scrubbed: "2,4";"foo";"foo.doc";"34567";"foo7";"foo7.doc";"45678";"foo6";"foo6.doc";"56789";"foo5";"foo5.doc";"67890";"foo4";"foo4.doc";"23456"    
  tokens: 16
   tok01: 23456
scrubbed: "3,0";"foo7";"foo7.doc";"34567"
  tokens: 4
   tok01: 34567
scrubbed: "3,0";"foo6";"foo6.doc";"45678"
  tokens: 4
   tok01: 45678
scrubbed: "3,0";"foo5";"foo5.doc";"56789"
  tokens: 4
   tok01: 56789
scrubbed: "3,0";"foo4";"foo4.doc";"67890"               
  tokens: 4
   tok01: 67890

When using nextToken() what is the starting token supposed to be? It appears as though StringTokenizer starts with token 0, so that the nextToken() is actually token 1 -- the second physical token. I did not see a firstToken() method in Java documentation, nor did I see a way to assign specific tokens to specific variables (e.g., String myToken = strTok.tokenNumber(0) etc.). What do I need to do to access the first physical token in my String?

Upvotes: 1

Views: 5897

Answers (4)

Udo Klimaschewski
Udo Klimaschewski

Reputation: 5315

Your code does not reflect the output, but anyhow you might want to use the String.split() functions instead of a tokenizer, when you want to access an arbitrary token, e.g.:

    String st = "a;b;c";        
    String[] tokens = st.split(";");
    System.out.println(tokens[0]);

will print out "a", the first token.

The StringTokenizer class allows only to access token after token, you cannot access a token in a random access way. But you can use it also to access the first token:

    String st = "a;b;c";        
    StringTokenizer tokenizer = new StringTokenizer(st,";");
    System.out.println(tokenizer.nextToken());

Will also print out "a", the first token.

Upvotes: 5

Prabhakaran Ramaswamy
Prabhakaran Ramaswamy

Reputation: 26094

The problem here is you printing the System.out.println(" tok01: " + tok01); out of while loop

  StringTokenizer strTok = new StringTokenizer(scrubbedInput, ";", false);
  int tokens = strTok.countTokens();
  while (strTok.hasMoreTokens()) {
    tok01 = strTok.nextToken();// here is the problem
  }
  System.out.println("  scrubbed: " + scrubbedInput);
  System.out.println("    tokens: " + tokens);
  System.out.println("     tok01: " + tok01);

I think it should be like below

   StringTokenizer strTok = new StringTokenizer(scrubbedInput, ";", false);
   int tokens = strTok.countTokens();
   System.out.println("  scrubbed: " + scrubbedInput);
   System.out.println("    tokens: " + tokens);
   while (strTok.hasMoreTokens()) {
       tok01 = strTok.nextToken();           
       System.out.println("     tok01: " + tok01);
   }

Upvotes: 0

Bhanu Kaushik
Bhanu Kaushik

Reputation: 864

Your while loop iterates over all tokens first i think it is a misplaced }.

    while (strTok.hasMoreTokens()) {
      tok01 = strTok.nextToken();                  
      System.out.println("     tok01: " + tok01);
    }

Upvotes: -1

MrSmith42
MrSmith42

Reputation: 10151

You overwrite the value of tokens in your loop.

Try this and have a look at the output.

public class parse {
  public static void main(String args[]) {
    FileInputStream inputStream = new FileInputStream("whidata0.txt");
    BufferedReader br = new BufferedReader(new InputStreamReader(inputStream)); 
    while((scrubbedInput=br.readLine())!=null) {
      StringTokenizer strTok = new StringTokenizer(scrubbedInput, ";", false);
      int tokens = strTok.countTokens();
      while (strTok.hasMoreTokens()) {
        tok01 = strTok.nextToken();
        System.out.println("     tok01: " + tok01);
      }
      System.out.println("  scrubbed: " + scrubbedInput);
      System.out.println("    tokens: " + tokens);
      System.out.println("last tok01: " + tok01);
    }
  }
}

Upvotes: 1

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