Writing applications instead of applets so our programs are
allowed to manipulate filesTopReading and writing files

Reading and writing files

To read from a file:

Here is some code from the Short words demo that does all of these steps:

// Open the file
wordReader = new BufferedReader(new FileReader(DICTIONARY_FILE));

// get the first line of the file
words[numWords] = wordReader.readLine();
			
// Read words until we run out of words or the array becomes full
while (words[numWords] != null && numWords < MAX_WORDS) {
   // Display the word
   allWordsArea.append(words[numWords] + "\ n");
   numWords++;

   // get the next line from the file
   words[numWords] = wordReader.readLine();
}

wordReader.close();

Lots of things can go wrong working with files. For example,

Because of these problems, file operations are generally surrounded by a try statement so these exceptions (IOException) can be handled. These exceptions are a little different than other exceptions we have seen this semester. These are checked exceptions, meaning that Java requires us to handle them. If we don't we will get a compiler error.

Writing a file requires similar steps:

Here is code from the ShortWords demo to write a file:

// open the stream to write to the file
FileWriter wordWriter = new FileWriter(SHORT_WORDS_FILE);

// write the fixed length words
wordWriter.write(shortWordsArea.getText());
			
// Close the file
wordWriter.close();

This code would again be within a try statement to handle the IOExceptions that might occur. See the complete example for details.


Writing applications instead of applets so our programs are
allowed to manipulate filesTopReading and writing files