Java File I/O

Java I/O is very interesting and much discussed feature of JAVA. There are few open-source library as well to make programmer's life easy. Here I will discuss only file reading example.

My favorite way to read a small file is to use a BufferedReader and a StringBuilder. It is very simple and to the point (though not particularly effective, but good enough for most cases):

    BufferedReader br = new BufferedReader(new FileReader("file.txt"));
    try {
        StringBuilder sb = new StringBuilder();
        String line = br.readLine();

        while (line != null) {
            sb.append(line);
            sb.append("n");
            line = br.readLine();
        }
        String everything = sb.toString();
    } finally {
        br.close();
    }

When I read strings like this, I usually want to do some string handling per line anyways, so then I go for this implementation.

One more way is to use the Scanner class in Java and the FileReader object simple exameple :

Scanner in = new Scanner(new FileReader("filename.txt"));

Scanner has several methods for reading in strings, numbers, etc... You can look for more info on this on the Java documentation page.

Though if I want to actually just read a file into a String I always use Apache Common IO with the class IOUtils.toString() method. You can have a look at the source here:

FileInputStream inputStream = new FileInputStream("foo.txt");
try { 
String everything = IOUtils.toString(inputStream); 
}
finally { 
inputStream.close();
}

Below two links can be referred for more information on methods and examples.

http://commons.apache.org/io/description.html

http://download.oracle.com/javase/tutorial/essential/io/file.html