You don't need to save the content of the file into an Object. By looking at the JavaDocs, you can see that the methods of Scanner support regex.
Just read and search:
File file = new File("file.txt");
Scanner scanner = null;
try
{
scanner = new Scanner(file);
}
catch (FileNotFoundException e){}
int i = 0;
while(scanner.hasNext("word"))
{
scanner.next("word");
i++;
}
System.out.println(i +" occurances of the word 'word'");