Java For Python Programmers Edition 2

File handling is an integral part of programming. Most programming languages have the ability to create, read from, write to, and delete, files. In Python, most built-in libraries are available without needing to explicitly import additional packages, but some libraries like math do need to be imported. Consider the following.

Delete the first line that says import math and see what happens. The import math is needed. The same program in Java would look like this:

Note the use of import java.lang.Math; in the above to import the Math class. Unlike Python, Java requires explicit import for most libraries, including the Math class and many classes related to file handling.

Much like the Math class, in order for your program to work with files you need use import. Java includes a class called File in the io library. This class allows you to create File objects, and use its public methods.

import java.io.File;

The Scanner class from the util library will need to be imported if there is any need for a program to read a file. It should be noted that this library is unnecessary if the program will not be reading any data from a file.

import java.util.Scanner;

The FileWriter class can be used to write to files. In the same way that the Scanner class isn’t needed unless the program will read from a file, the FileWriter class isn’t needed unless the program will write to a file.

import java.io.FileWriter;

Finally, these last two classes provide error handling and must be used in tandem with the File class when reading from or writing to files. IOException handles file creation and writing errors, while FileNotFoundException handles errors when trying to read files.

import java.io.IOException;
import java.io.FileNotFoundException;