File I/O - Absolute Java - page 616

Display 10.14 Some Methods in the Class ObjectOutputStream (part 2 of 2)

public void writeFloat( float x) throws IOException

Writes the float value x to the output stream.

public void writeChar( int n) throws IOException

Writes the char value n to the output stream. Note that it expects its argument to be an int
value. However, if you simply use the char value, then Java will automatically type cast it to an
int value. The following are equivalent:
outputStream.writeChar(( int )'A');

and

outputStream.writeChar('A');
public void writeUTF(String aString) throws IOException

Writes the String value aString to the output stream. UTF refers to a particular method of
encoding the string. To read the string back from the file, you should use the method readUTF of
the class ObjectInputStream .

public void writeObject(Object anObject) throws IOException
Writes its argument to the output stream. The object argument should be an object of a serializable
class, a concept discussed later in the section titled “The Serializable Interface.” Throws
various IOExceptions .
public void close() throws IOException

Closes the stream's connection to a file. This method calls flush before closing the file.

public void flush() throws IOException
Flushes the output stream. This forces an actual physical write to the file of any data that has been
buffered and not yet physically written to the file. Normally, you should not need to invoke flush .

Notice that almost all the code in the sample program in Display 10.13 is in a try
block. Any part of the code that does binary file I/O in the ways we are describing can
throw an IOException .
The output stream for writing to the binary file numbers.dat is created and named
with the following:

ObjectOutputStream outputStream =
new ObjectOutputStream( new
FileOutputStream("numbers.dat"));
As with text files, this is called opening the file . If the file numbers.dat does not
already exist, this statement will create an empty file named numbers.dat . If the file
numbers.dat already exists, this statement will erase the contents of the file so that the
file starts out empty. The situation is basically the same as what you learned for text
files, except that we are using a different class.

opening a file