I have searched the site and have found some answers, but i'm having trouble understanding the difference between these two classes. Can someone explain the differences between these two classes?
PrintStreams can allow more flexibility with encoding. I'm guessing that some system encodings are used, but I'm not sure. PrintWriter is also about twice as fast for printing text.
PrintStream ) enables you to write formatted data to an underlying OutputStream . The PrintStream class can format primitive types like int , long etc. formatted as text, rather than as their byte values.
println is preferred when we have to print a lot of items as PrintWriter is faster than the other to print data to the console.
OutputStreams are meant for binary data. Writers (including PrintWriter ) are meant for text data. You may not see the difference in your specific situation as you're calling PrintWriter.
PrintStream
was the original bridge to deal with encoding characters and other datatypes. If you look at the javadoc for java.io.OutputStream
you'll see methods only for writing two distinct data types: byte
and int
.
In early versions of the JDK (1.0.x), when you wanted to write characters, you could do one of two things, write bytes to an output stream (which are assumed to be in the system default character set):
outputStream.write("foobar".getBytes());
or wrap another outputStream
in a PrintStream
:
PrintStream printStream = new PrintStream(outputStream); printStream.write("foobar");
See the difference? PrintStream
is handling the character conversion to bytes, as well as encoding (the constructor call above uses the system default encoding, but you could pass it as a parameter). It also provides convenience methods for writing double
, boolean
, etc....
In fact System.out
and System.err
are defined as PrintStream
instances.
Along comes JDK 1.1, and they realize they need a better way to deal with pure character data, since PrintStream
still has the byte based methods for writing. So they introduced the Writer
abstract class to deal strictly with char
, String
and int
data.
PrintWriter
adds methods for other types like double
, boolean
, etc...
Nowadays PrintWriter
also has format()
/ printf()
methods for format printing, etc...
As a general rule, if you're writing character data, use Writer
instances. If you're writing binary (or mixed) data use OutputStream
instances.
From the Javadoc for PrintWriter:
Prints formatted representations of objects to a text-output stream. This class implements all of the print methods found in PrintStream. It does not contain methods for writing raw bytes, for which a program should use unencoded byte streams.
Think of it this way: a PrintStream
sits on top of some OutputStream
. Since output streams deal with bytes rather than characters, the PrintStream must take responsibility for encoding characters into bytes. The OutputStream 'merely' writes the bytes out to a file/console/socket whatever.
A PrintWriter
, on the other hand, sits on top of a Writer
. Since the Writer is responsible for encoding characters into bytes, the PrintWriter does not do encoding. I just knows about newlines etc. (Yes, PrintWriters do have constructors that take File
s and OutputStream
s, but those are simply conveniences. For example, PrintWriter(OutputStream)
.
Creates a new PrintWriter, without automatic line flushing, from an existing OutputStream. This convenience constructor creates the necessary intermediate OutputStreamWriter, which will convert characters into bytes using the default character encoding.
BTW, In case you are thinking that the PrintWriter
really doesn't have much utility, remember that both PrintWriter and PrintStream absorb IOException
s from printing logic.
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