Finding words in text

The standard Java libraries offer support for searching through text for specific tokens. In previous examples, we have demonstrated the matches method and regular expressions, which can be useful when searching text. In this example, however, we will demonstrate a simple technique using the contains method and the equals method to locate a particular string. First, we normalize our text and the word we are searching for to ensure we can find a match. We also create an integer variable to hold the number of times the word is found:

dirtyText = dirtyText.toLowerCase().trim(); 
toFind = toFind.toLowerCase().trim(); 
int count = 0; 

Next, we call the contains method to determine whether the word exists in our text. If it does, we split the text into an array and then loop through, using the equals method to compare each word. If we encounter the word, we increment our counter by one. Finally, we display the output to show how many times our word was encountered:

 
if(dirtyText.contains(toFind)){ 
      String[] words = dirtyText.split(" "); 
      for(String word : words){ 
            if(word.equals(toFind)){ 
                  count++; 
            } 
      } 
out.println("Found " + toFind + " " + count + " times in the text."); 
} 

In this example, we set toFind to the letter I. This produced the following output:

Found i 2 times in the text.

We also have the option to use the Scanner class to search through an entire file. One helpful method is the findWithinHorizon method. This uses a Scanner to parse the text up to a given horizon specification. If zero is used for the second parameter, as shown next, the entire Scanner will be searched by default:

dirtyText = dirtyText.toLowerCase().trim();  
toFind = toFind.toLowerCase().trim(); 
Scanner textLine = new Scanner(dirtyText); 
out.println("Found " + textLine.findWithinHorizon(toFind, 10)); 

This technique can be more efficient for locating a particular string, but it does make it more difficult to determine where, and how many times, the string was found.

It can also be more efficient to search an entire file using a BufferedReader. We specify the file to search and use a try-catch block to catch any IO exceptions. We create a new BufferedReader object from our path and process our file as long as the next line is not empty:

String path = "C:// MobyDick.txt"; 
try { 
    String textLine = ""; 
    toFind = toFind.toLowerCase().trim(); 
    BufferedReader textToClean = new BufferedReader( 
        new FileReader(path)); 
    while((textLine = textToClean.readLine()) != null){ 
        line++; 
        if(textLine.toLowerCase().trim().contains(toFind)){ 
            out.println("Found " + toFind + " in " + textLine); 
           } 
    } 
    textToClean.close(); 
} catch (IOException ex) { 
    // Handle exceptions 
} 

We again test our data by searching for the word I in the first sentences of Moby Dick. The truncated output follows:

Found i in Call me Ishmael...