Writing text files

To write a string of text on a file we have to do the following:

1. open the file for writing by creating an object of the class FileWriter associated to the name of the file, and creating an object of the class PrintWriter associated to the FileWriter object just created;
2. write text on the file by using the print and println methods of the PrintWriter object;
3. close the file when we are finished writing to it.

The Java statements that realize the three phases described above are:

// 1. opening the file for writing (creation of the file)
FileWriter f = new FileWriter("test.txt");
PrintWriter out = new PrintWriter(f);

// 2. writing text on the file
out.println("some text to write to the file");

// 3. closing the output channel and the file
out.close();
f.close();

Notes:

• The invocation of the constructor of the class FileWriter has the effect of creating a file that is ready to be written on. If the file already exists, all its contents is erased first.
• To append text to an already existing file without erasing the previous content of the file, we have to use the constructor with the signature FileWriter(String, boolean), specifying the value true for the second argument.