printf : Java Glossary

2008-04-24 by Roedy Green ©1996-2008 Canadian Mind Products
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printf

Java 1.5+, java.io.PrintWriter. printf, java.io.PrintStream. printf and the java.util. Formatter class give you abilities similar to C’s printf. You can also use String. format to build a String using the formatting scheme. It was added in response to C++ programmers coming to Java who wanted their familiar formatting tools. Don’t confuse printf and print/println.

It is particularly useful for making listings line up by assigning fixed widths to your fields or for displaying in hex. G format gives you an ability like the G format in FØRTRAN, which will display in F format or E format as appropriate.

The java.text.DecimalFormat and java.text.NumberFormat classes in JDK 1.1+ give you similar ability a bit more verbosely. Java 1.0.2 has no equivalent to the C printf or sprintf function for formatting numbers for display. You have to roll your own. One such class is available from San Diego State University called sdsu.FormatString. Acme also has one. Eliote Rusty Harold did one. Gary Cornell and Cay Horstmann’s book Core Java 2 includes one.

Most people don’t bother with printf. They use the + concatenation operator instead of printf.

// in idiomatic Java you would say:
System.out.println( "x:" + x + " y:" + y );

// instead of C-style
System.out.printf( "x: %d y: %d", x, y );

Books

recommend book⇒Core Java 2, Volume I: Fundamentals (6th Edition)

paperback

ISBN10:

0-13-047177-1

ISBN13:

978-0-13-047177-2

publisher:

Prentice Hall

published:

2002-08-22

by:

Cay Horstmann and Gary Cornell

Covers JDK 1.4 such as regular expressions, New I/O, assertions, Preferences, Swing enhancements and logging. Aimed at someone who already knows C++. This is not a fluffy introductory book.

	amazon.ca	amazon.com
	chapters.indigo.ca	powells.com
	amazon.fr	barnesandnoble.com
	amazon.de	amazon.co.uk

Learning More

Sun’s Javadoc on PrintWriter.printf : available:

on the web at java.Sun.com
in the JDK 1.6.0_06 or in the older JDK 1.5.0_15 or the even older JDK 1.4.2_17 on your local J: drive.

Sun’s Javadoc on PrintStream.printf : available:

on the web at java.Sun.com
in the JDK 1.6.0_06 or in the older JDK 1.5.0_15 or the even older JDK 1.4.2_17 on your local J: drive.

Sun’s Javadoc on the Formatter class : available:

on the web at java.Sun.com
in the JDK 1.6.0_06 or in the older JDK 1.5.0_15 or the even older JDK 1.4.2_17 on your local J: drive.

Sun’s Javadoc on String.format : available:

on the web at java.Sun.com
in the JDK 1.6.0_06 or in the older JDK 1.5.0_15 or the even older JDK 1.4.2_17 on your local J: drive.

DecimalFormat
format
NumberFormat
println format
Sun’s old unofficial sprintf

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