Commit f79fe09

Java has several libraries included for file handling, though, they must be imported. Java includes a class called File in the io library. The class can be imported with the following line. Be sure to capitalize 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.

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.

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.

Before we can write code that creates a file, we must first import the necessary classes mentioned in the previous section (Scanner and FileWriter are not needed for a class that only creates files) and create a class. We will call this class CreateFile.

Next, within the main function, we will create a File object. It is important to create a meaningful name for the File object. We will call ours <c>myFile</c>.

myFile is the name of the object within the program, while "myfile.txt" is the name of the file itself and will be the file name if the operation that creates the file is successful.

Now that we have created a new File object, we can create a file using the <c>createNewFile()</c> method from the File class. While the previous line of code creates an object within the program for the file, this method actually does the work of creating a file and saving it in the current working directory. This method returns a boolean value. If the method returns <c>true</c>, the file was successfully created. If the method returns <c>false</c>, there is already a file using the chosen file name. We can use this method's possible return values in tandem with an if/else selection to determine if the file was created, or if a file with that file name already exists in the directory.

<program language="python">

The code may seem complete at this point, but if you remember from the previous section, error handling using the IOException is required for program to compile. Let's utilize best practices and add in try/catch blocks to handle exceptions thrown by the IOException class.

The <c>IOException e</c> part in the parenthesis next to the catch. This creates a variable called <c>e</c> that refers to an IOException object. In other words, <c>e</c> refers to the error created if the try block fails. The line <c>e.printStackTrace();</c> prints the stack trace to the console. This is what the console may output if the program tries to create a file, but is blocked by the Operating System due to insufficient permissions:

<program language="python">

You may be wondering: "What if I don't want to create a file in the current working directory?" Good question! In Windows environments, you can specify the file path using two back slashes for each back slash in the file path. For each pair of back slashes, the first backslash acts as an escape character. So, if you want to save a file to this directory:

The <c>createNewFile()</c> method is useful for attempting to create files and reporting if the operation was successful, however, <c>createNewFile()</c> does not write anything to files it creates. In fact, if you use <c>createNewFile()</c> to create a .txt file and then open the file, the file will be blank.

To write to a file, we will need to create a different class. We will do the same setup as the previous section. First, we will import the classes (File and Scanner are not needed) and create the framework for a class that will write to a file. Let's call this class WriteFile:

Next, we will create a FileWriter object. Let's call it myWriter:

In this next step, we will use the <c>write()</c> method from the FileWriter class. This Method will take any data within the parenthesis and write that data to the file selected. The write() method takes most standard data types:

Next, we will again add the required try/catch blocks utilizing the IOException class. Just like with creating files, the program will not compile without these crucial additions! We will also add some print statements to inform us of the success of the file write operation. First, a Python example:

<program language="python">

<program language="python">

If a file does not already exist (for example, myfile.txt does not exist), the <c>write()</c> method will create the file. Despite this, it is still a good idea to create separate methods or classes for creating and writing to files. Not only is it good practice to ensure methods only accomplish one thing, but the <c>createNewFile()</c> method avoids overwriting files that already exist. Imagine a file with the name myfile.txt already exists and contains important information. Attempting to create a file using the <c>write()</c> method will delete that data forever.

Speaking of overwriting data, what if we want to append text to the end of any text already in myfile.txt? To accomplish this, we can pass a boolean argument along with the file name when creating a new data argument:

and then run the program twice, the contents of myfile.txt would be:

<program language="python">

<program language="python">