In this tutorial, we show you how to read from and write to text or character files using classes available in the java. It implements the following fundamental methods: InputStreamReader is a bridge from byte streams to character streams.
Our first example will be a program that writes a string to a file. For those familiar with C, a FileOutputStream is analogous to a file handle. When we send a stream or sequence of data to the FileOutputStream handle, data will be written to disk. In Java, there exists a large number of extensions to the standard input and output stream classes.
This is handy, as the basic input and output streams deal only with the transfer of bytes - not the easiest way for us to write out data. There's a wide variety of streams to choose from: In this case, we wish to write a string to the file, and so we create a new PrintStream object that takes as its constructor the existing FileOutputStream.
Any data we send from PrintStream will now be passed to the FileOutputStream, and ultimately to disk. We then make a call to the println method, passing it a string, and then close the connection.
Rather than checking for erroneous return values such as a null pointer when obtaining an output stream as is the case with C's fopenwe catch exceptions. Exceptions are events that occur in exceptional or unusual circumstances, such as error conditions. A method can throw an exception, to indicate to the calling object that a non-standard circumstance has occurred.
Thus, instead of checking each and every file method call, we have one piece of code handling all possible errors!
File input File input under Java differs little from file output.
In this example, the file we open is given to us as the first command line parameter. We obtain this by examining the args array of strings.
Since an array is an actual object in Java, we can find the length of the array and hence the number of parameters through the length attribute. To do anything useful with file input, we create a DataInputStream which can handle reading in data as well as lines of text.
To determine if there is any data left to read, we call the available method of our input stream. This method returns the number of bytes remaining, which we check to see is not equal to zero.
Then we call the DataInputStream's readLine method and print the result to the screen. There are a wide variety of methods supported by the DataInputStream class, which make it easy to read in almost any data type. For further information, consult your Java API. In the next installment of this tutorial series, we'll be covering some of the more advanced object-orientated features of Java - in particular the way in which classes can be extended through inheritance.Java provides several ways to write to file.
We can use FileWriter, BufferedWriter, java 7 Files and FileOutputStream to write file in Java. Java Write to File. I would like to add a bit more to MadProgrammer's Answer. In case of multiple line writing, when executing the command.
ph-vs.com(string); one may notice that the newline characters are omitted or skipped in the written file even though they appear during debugging or if the same text is printed onto the terminal with.
You can read from (or write to) a text file using the Open statement, Close statement and various other statements for actually reading/writing.
The Open statement has clauses for what type of access you want to the file, so you can specify if you want to read it as text, write to it as binary, and so on. You can also set locking options, to stop other programs from opening the file.
Wouldn’t that write the text all one line; even if content included a larger amount of text on different lines? I’m working in similar code and trying to write to file using text from a TextField but it put all the text . I would like to add a bit more to MadProgrammer's Answer.
In case of multiple line writing, when executing the command. ph-vs.com(string); one may notice that the newline characters are omitted or skipped in the written file even though they appear during debugging or if the same text is printed onto the terminal with. In this tutorial, we show you how to read from and write to text (or character) files using classes available in the ph-vs.com package.
First, let’s look at the different classes that are capable of reading and writing character streams.