Java The Complete Reference, Seventh Edition

574 Part II: The Java Library

}

input.close();

}

}

This example creates aVectorand then adds two filenames to it. It passes that vector of

names to theInputStreamEnumeratorclass, which is designed to provide a wrapper on the

vector where the elements returned are not the filenames but rather, openFileInputStreams

on those names. TheSequenceInputStreamopens each file in turn, and this example prints

the contents of the two files.

PrintStream

ThePrintStreamclass provides all of the output capabilities we have been using from the

Systemfile handle,System.out, since the beginning of the book. This makesPrintStream

one of Java’s most often used classes. It implements theAppendable,Closeable, and

Flushableinterfaces.

PrintStreamdefines several constructors. The ones shown next have been specified

from the start:

PrintStream(OutputStreamoutputStream)

PrintStream(OutputStreamoutputStream, booleanflushOnNewline)

PrintStream(OutputStreamoutputStream, booleanflushOnNewline,

StringcharSet)

Here,outputStreamspecifies an openOutputStreamthat will receive output. TheflushOnNewline

parameter controls whether the output buffer is automatically flushed every time a newline

(\n) character or a byte array is written, or whenprintln( )is called. IfflushOnNewlineis

true, flushing automatically takes place. If it isfalse, flushing is not automatic. The first

constructor does not automatically flush. You can specify a character encoding by passing

its name incharSet.

The next set of constructors give you an easy way to construct aPrintStreamthat writes

its output to a file.

PrintStream(FileoutputFile) throws FileNotFoundException

PrintStream(FileoutputFile, StringcharSet)

throws FileNotFoundException, UnsupportedEncodingException

PrintStream(StringoutputFileName) throws FileNotFoundException

PrintStream(StringoutputFileName, StringcharSet)

throws FileNotFoundException, UnsupportedEncodingException

These allow aPrintStreamto be created from aFileobject or by specifying the name of a

file. In either case, the file is automatically created. Any preexisting file by the same name is

destroyed. Once created, thePrintStreamobject directs all output to the specified file. You

can specify a character encoding by passing its name incharSet.

PrintStreamsupports theprint( )andprintln( )methods for all types, includingObject.

If an argument is not a primitive type, thePrintStreammethods will call the object’stoString( )

method and then display the result.