It converts the double argument to a long using the doubleToLongBits method in class Double, and then writes that long value to the file as an eight-byte quantity, high byte first. It sets the file-pointer offset, measured from the beginning of this file, at which the next read or write occurs. It reads a signed 32-bit integer from this file. It returns the unique FileChannel object associated with this file. It closes this random access file stream and releases any system resources associated with the stream. RandomAccessFile(String name, String mode)Ĭreates a random access file stream to read from, and optionally to write to, a file with the specified name. Constructor ConstructorĬreates a random access file stream to read from, and optionally to write to, the file specified by the File argument. If end-of-file is reached before the desired number of byte has been read than EOFException is thrown. There is a cursor implied to the array called file pointer, by moving the cursor we do the read write operations. A random access file behaves like a large array of bytes. If you have any questions, just leave a note in the Comments section.This class is used for reading and writing to random access file.
I hope this Java file-open and file-read example has been helpful. Java file read and open example - Summary You can also use some methods of the Java File class to test that the file exists and is readable, but I've skipped those steps in this example, as those problems will be caught with the try/catch statement. For more information about this, see my Java FileReader examples/tutorial and my Java BufferedReader examples. The BufferedReader also gives you the convenient readLine method. I don't know why a FileReader doesn't handle buffering, but it doesn't, so you add the BufferedReader to make it much faster to read larger files.
You want to use both a BufferedReader and FileReader like this when reading from a text file in Java. (As a side note, if you're interested in formatting your text output, note that I use to print my error output.) Opening a text file with JavaĪs you can see from the example, I open the text file using this line of code: Note that when I read and open the file, I just catch any errors that may occur with a generic Exception object, but if you need to handle more specific problems you can catch the individual IOException and FileNotFoundException objects. ("Exception occurred trying to read '%s'.", filename) While ((line = reader.readLine()) != null) * (Demonstrates Java FileReader, BufferedReader, and Java5.)īufferedReader reader = new BufferedReader(new FileReader(filename)) * Open and read a file, and return the lines in the file as a list In the following Java method, the file is opened with the Java FileReader and BufferedReader, and then, as each line of the file is read it is assigned to a Java String, with each String in turn being added to an ArrayList named records. This uses the most recent Java syntax and classes.
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Solution: Here’s a method taken from a Java class I wrote that shows how to open and read a file using the Java FileReader class. Java File I/O FAQ: How do I open a file and read text from it using Java? (Also written as, “How do I use the Java BufferedReader and FileReader classes to read from a text file?”)
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