"jar --update" - Updating Class Files in JAR

This section provides a tutorial example on how to 'jar --update' to update class files in JAR files.

If you have an existing JAR file, you can use the "jar --update" command to update (add or replace) class files in the JAR file.

Here is what I did to add F2C.class to herong.jar:

herong> jar --update --verbose --file herong.jar F2C.class

herong> jar --list --verbose --file herong.jar
     0 ... EDT 2018 META-INF/
    66 ... EDT 2018 META-INF/MANIFEST.MF
     0 ... EDT 2018 com/
     0 ... EDT 2018 com/herongyang/
   806 ... EDT 2018 com/herongyang/TempratureConvertorBean.class
  1208 ... EDT 2018 F2C.class

Note that F2C.class is stored in the root directory of the JAR file, since it is an un-named package class.

Now I can move herong.jar to any where, and run the F2C class from the JAR file:

herong> del F2C.class

herong> java -classpath herong.jar F2C 70
Fahrenheit = 70.0
Celsius = 21.11111111111111
My TempraturConvertorBean - Version 1.00

Basically, a JAR file is a container of Java class files.

Table of Contents

 About This Book

 Java Tools Terminology

 Java Tools Included in JDK

 javac - The Java Program Compiler

jar - The JAR File Tool

 JAR - Java Archive File Format

 jar - JAR File Tool Command and Options

 "jar --create" - Creating New JAR File

 "jar --list" - Listing Files in JAR File

 "jar --extract" - Extracting Files from JAR File

 Managing JAR Files with WinZIP

 META-INF/MANIFEST.MF - JAR Manifest File

 Adding META-INF/MANIFEST.MF to JAR Files

 "jar -C" - Changing Input Directory

 Using JAR Files in Java Class Paths

"jar --update" - Updating Class Files in JAR

 "jar --main-class" - Making JAR File Executable

 Creating Module JAR File

 "jar --module-version" - Updating Module Version in JAR

 jlink - The JRE Linker

 jmod - The JMOD File Tool

 jimage - The JIMAGE File Tool

 jpackage - Binary Package Builder

 java - The Java Program Launcher

 jdeps - The Java Class Dependency Analyzer

 jdeprscan - The Java Deprecated API Scanner

 jdb - The Java Debugger

 jcmd - The JVM Diagnostic Tool

 jconsole - Java Monitoring and Management Console

 jstat - JVM Statistics Monitoring Tool

 JVM Troubleshooting Tools

 jhsdb - The Java HotSpot Debugger

 jvisualvm (Java VisualVM) - JVM Visual Tool

 jmc - Java Mission Control

 javap - The Java Class File Disassembler

 keytool - Public Key Certificate Tool

 jarsigner - JAR File Signer

 jshell - Java Language Shell

 jrunscript - Script Code Shell

 serialver - serialVersionUID Generator

 native2ascii - Native-to-ASCII Encoding Converter

 Outdated Tutorials

 References

 Full Version in PDF/EPUB