Java - StreamTokenizer resetSyntax() method

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Description

The Java StreamTokenizer resetSyntax() method resets this tokenizer's syntax table so that all characters are "ordinary." See the ordinaryChar method for more information on a character being ordinary.

Declaration

Following is the declaration for java.io.StreamTokenizer.resetSyntax() method.

public void resetSyntax()

Parameters

NA

Return Value

This method does not return a value.

Exception

NA

Example - Usage of StreamTokenizer resetSyntax() method

The following example shows the usage of StreamTokenizer resetSyntax() method.

StreamTokenizerDemo.java

package com.tutorialspoint;

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStreamReader;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Reader;
import java.io.StreamTokenizer;

public class StreamTokenizerDemo {
   public static void main(String[] args) {
      String text = "Hello. This is a text \n that will be split "
         + "into tokens. 1 + 1 = 2";
         
      try {
         // create a new file with an ObjectOutputStream
         FileOutputStream out = new FileOutputStream("test.txt");
         ObjectOutputStream oout = new ObjectOutputStream(out);

         // write something in the file
         oout.writeUTF(text);
         oout.flush();

         // create an ObjectInputStream for the file we created before
         ObjectInputStream ois = new ObjectInputStream(new FileInputStream("test.txt"));

         // create a new tokenizer
         Reader r = new BufferedReader(new InputStreamReader(ois));
         StreamTokenizer st = new StreamTokenizer(r);

         // print the stream tokens
         boolean eof = false;
         
         do {
            int token = st.nextToken();

            switch (token) {
               case StreamTokenizer.TT_EOF:
                  System.out.println("End of File encountered.");
                  eof = true;
                  break;
                  
               case StreamTokenizer.TT_EOL:
                  System.out.println("End of Line encountered.");
                  break;
                  
               case StreamTokenizer.TT_WORD:
                  System.out.println("Word: " + st.sval);
                  break;
                  
               case StreamTokenizer.TT_NUMBER:
                  // when a number is met, reset syntax
                  st.resetSyntax();
                  System.out.println("Number: " + st.nval);
                  break;
                  
               default:
                  System.out.println((char) token + " encountered.");
                  
                  if (token == '!') {
                     eof = true;
                  }
            }
         } while (!eof);

      } catch (Exception ex) {
         ex.printStackTrace();
      }
   }
}

Output

Let us compile and run the above program, this will produce the following result −

Word: AHello.
Word: This
Word: is
Word: a
Word: text
Word: that
Word: will
Word: be
Word: split
Word: into
Word: tokens.
Number: 1.0
  encountered.
+ encountered.
  encountered.
1 encountered.
  encountered.
= encountered.
  encountered.
2 encountered.
End of File encountered.

Example - Parse only lowercase letters as words

The following example shows the usage of StreamTokenizer resetSyntax() method.

StreamTokenizerDemo.java

package com.tutorialspoint;

import java.io.IOException;
import java.io.Reader;
import java.io.StreamTokenizer;
import java.io.StringReader;

public class StreamTokenizerDemo {
   public static void main(String[] args) throws IOException {
      String input = "abc DEF 123";

      Reader reader = new StringReader(input);
      StreamTokenizer tokenizer = new StreamTokenizer(reader);

      tokenizer.resetSyntax(); // Clear all syntax
      tokenizer.wordChars('a', 'z'); // Only lowercase letters are word characters
      tokenizer.whitespaceChars(' ', ' '); // Space is whitespace

      System.out.println("Tokens:");
      while (tokenizer.nextToken() != StreamTokenizer.TT_EOF) {
         if (tokenizer.ttype == StreamTokenizer.TT_WORD) {
            System.out.println("Word: " + tokenizer.sval);
         } else {
            System.out.println("Char: " + (char) tokenizer.ttype);
         }
      }
   }
}

Output

Let us compile and run the above program, this will produce the following result−

Tokens:
Word: abc
Char: D
Char: E
Char: F
Char: 1
Char: 2
Char: 3

Explanation

• After resetSyntax(), only a−z are recognized as word characters.

• DEF and 123 are treated as individual characters.

Example - Parse digits only, everything else is ignored or treated literally

The following example shows the usage of StreamTokenizer resetSyntax() method.

StreamTokenizerDemo.java

package com.tutorialspoint;

import java.io.IOException;
import java.io.Reader;
import java.io.StreamTokenizer;
import java.io.StringReader;

public class StreamTokenizerDemo {
   public static void main(String[] args) throws IOException {
      String input = "abc123XYZ";

      Reader reader = new StringReader(input);
      StreamTokenizer tokenizer = new StreamTokenizer(reader);

      tokenizer.resetSyntax(); // Reset all defaults
      tokenizer.wordChars('0', '9'); // Only digits are word characters

      System.out.println("Tokens:");
      while (tokenizer.nextToken() != StreamTokenizer.TT_EOF) {
         if (tokenizer.ttype == StreamTokenizer.TT_WORD) {
            System.out.println("Number: " + tokenizer.sval);
         } else {
            System.out.println("Char: " + (char) tokenizer.ttype);
         }
      }
   }
}

Output

Let us compile and run the above program, this will produce the following result−

Tokens:
Char: a
Char: b
Char: c
Number: 123
Char: X
Char: Y
Char: Z

Explanation

• Only digits are treated as part of a word token.

• All other characters are treated literally.