Java How to Program Fourth Edition - DCC

576 Strings and Characters Chapter 10
The condition in the if structure on line 23 uses method equals to determine
whether the object c1 has the same contents as the object c2 (i.e., the characters inside
each object are equal).
10.20 Class StringTokenizer
When you read a sentence, your mind breaks the sentence into individual words and punctuation,
or tokens, each of which conveys meaning to you. Compilers also perform tokenization.
They break up statements into individual pieces like keywords, identifiers,
operators and other elements of a programming language. In this section, we study Java’s
StringTokenizer class (from package java.util), which breaks a string into its
component tokens. Tokens are separated from one another by delimiters, typically whitespace
characters such as blank, tab, newline and carriage return. Other characters can also
be used as delimiters to separate tokens. The program in Fig. 10.20 demonstrates class
StringTokenizer. The window for class TokenTest displays a JTextField
where the user types a sentence to tokenize. Output in this program is displayed in a
JTextArea.
When the user presses the Enter key in the JTextField, method actionPerformed
(lines 37–49) is invoked. Lines 39–40 assign String reference stringToTokenize
the value in the text in the JTextField returned by calling
event.getActionCommand(). Next, lines 41–42 create an instance of class
StringTokenizer. This StringTokenizer constructor takes a String argument
and creates a StringTokenizer for stringToTokenize that will use the default
delimiter string " \n\t\r" consisting of a space, a newline, a tab and a carriage return
for tokenization. There are two other constructors for class StringTokenizer. In the
version that takes two String arguments, the second String is the delimiter String.
In the version that takes three arguments, the second String is the delimiter String and
the third argument (a boolean) determines whether the delimiters are also returned as
tokens (only if the argument is true). This is useful if you need to know what the delimiters
are.
1 // Fig. 10.20: TokenTest.java
2 // Testing the StringTokenizer class of the java.util package
3
4 // Java core packages
5 import java.util.*;
6 import java.awt.*;
7 import java.awt.event.*;
8
9 // Java extension packages
10 import javax.swing.*;
11
12 public class TokenTest extends JFrame {
13 private JLabel promptLabel;
14 private JTextField inputField;
15 private JTextArea outputArea;
16
Fig. Fig. 10.20 10.20 Tokenizing strings with a StringTokenizer object (part 1 of 3).
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