Finding and replacing text

We often not only want to find text but also replace it with something else. We begin our next example much like we did the previous examples, by specifying our text, our text to locate, and invoking the contains method. If we find the text, we call the replaceAll method to modify our string:

text = text.toLowerCase().trim(); 
toFind = toFind.toLowerCase().trim(); 
out.println(text); 

if(text.contains(toFind)){ 
      text = text.replaceAll(toFind, replaceWith); 
      out.println(text); 
} 

To test this code, we set toFind to the word I and replaceWith to Ishmael. Our output follows:

call me ishmael. some years ago- never mind how long precisely - having little or no money in my purse, and nothing particular to interest me on shore, i thought i would sail about a little and see the watery part of the world.
call me ishmael. some years ago- never mind how long precisely - having little or no money in my purse, and nothing particular to interest me on shore, Ishmael thought Ishmael would sail about a little and see the watery part of the world.

Apache Commons also provides a replace method with several variations in the StringUtils class. This class provides much of the same functionality as the String class, but with more flexibility and options. In the following example, we use our string from Moby Dick and replace all instances of the word me with X to demonstrate the replace method:

out.println(text); 
out.println(StringUtils.replace(text, "me", "X")); 

The truncated output follows:

Call me Ishmael. Some years ago- never mind how long precisely -
Call X Ishmael. SoX years ago- never mind how long precisely -

Notice how every instance of me has been replaced, even those instances contained within other words, such as some. This can be avoided by adding spaces around me , although this will ignore any instances where me is at the end of the sentence, like me. We will examine a better alternative using Google Guava in a moment.

The StringUtils class also provides a replacePattern method that allows you to search for and replace text based upon a regular expression. In the following example, we replace all non-word characters, such as hyphens and commas, with a single space:

out.println(text); 
text = StringUtils.replacePattern(text, "\\W\\s", " "); 
out.println(text); 

This will produce the following truncated output:

Call me Ishmael. Some years ago- never mind how long precisely - 
Call me Ishmael Some years ago never mind how long precisely

Google Guava provides additional support for matching and modify text data using the CharMatcher class. CharMatcher not only allows you to find data matching a particular char pattern, but also provides options as to how to handle the data. This includes allowing you to retain the data, replace the data, and trim whitespaces from within a particular string.

In this example, we are going to use the replace method to simply replace all instances of the word me with a single space. This will produce series of empty spaces within our text. We will then collapse the extra whitespace using the trimAndCollapseFrom method and print our string again:

text = text.replace("me", " "); 
out.println("With double spaces: " + text); 
String spaced = CharMatcher.WHITESPACE.trimAndCollapseFrom(text, ' '); 
out.println("With double spaces removed: " + spaced); 

Our output is truncated as follows:

With double spaces: Call Ishmael. So years ago- ...
With double spaces removed: Call Ishmael. So years ago- ...