Arrays and Strings - Beginning Java - page 177

index = text.indexOf(andStr, index);

}

// Search backwards for "the"
index = text.lastIndexOf(theStr); // Find last 'the'
while(index >= 0) {
++theCount;
index -= theStr.length(); // Step to position before

last 'the'
index = text.lastIndexOf(theStr, index);

}
System.out.println("The text contains " + andCount + " ands\n"
+ "The text contains " + theCount + " thes");

}

FindCharacters.java

The program produces the following output:
The text contains 2 ands
The text contains 5 thes

NOTE Ifyouwereexpecting the "the" counttobe3,notethatthereisoneinstance
in "whether" and another in "them" . If you want to find three, you need to refine
your program to eliminate such pseudo-occurrences by checking the characters on
either side of the "the" substring.

How It Works
You define the String variable, text , as before, and set up two counters, andCount and theCount , for
the two words. The variable index keeps track of the current position in the string. You then have String
variables andStr and theStr holding the substrings you will be searching for.
To find the instances of "and" , you first find the index position of the first occurrence of "and" in the
string text . If this index is negative, text does not contain "and" , and the while loop does not execute,
as the condition is false on the first iteration. Assuming there is at least one "and" , the while loop block
executes and andCount is incremented for the instance of "and" you have just found. The indexOf()
method returns the index position of the first character of the substring, so you have to move the index
forward to the character following the last character of the substring you have just found. This is done by
adding the length of the substring, as shown in Figure 4-11 .

FIGURE 4-11