JDK : Java Glossary

acronym JDK (Java Development Kit). Formerly foppishly called the SDK (Software Development Kit). It is free, and you may freely distribute any programs you create with it.

• The most recent 1.7 JDK version is 1.7.0_21.
• The most recent 1.6 JDK version is 1.6.0_45.
• JET (Just Enough Time) 8.0 supports up to Java 1.6.0_43 though you can compile with javac.exe 1.7 with the -target 1.6 option.

To further confuse you, Oracle refers to the various downloads of Java updates. They are not updates, but entire new versions. You don’t need a previous version installed.

To use the JDK you must be running W2K/XP/W2003/Vista/W2008/W7-32/W7-64/W8-32/W8-64/Linux/LinuxARM/LinuxX86/LinuxX64/Ubuntu/Solaris/SolarisSPARC/SolarisSPARC64/SolarisX86/SolarisX64/OSX or Solaris.

Downloading the JDK

Below is how to get Java for Windows, Linux and Solaris. For other platforms (e.g. various Unices) see your OS (Operating System) vendor’s site. For example for NetBSD Unix Java is included in pkgsrc (the Packages System).

Version	Executables	Documentation	What’s New
JDK 1.7.0_21 (current)	JDK 1.7.0_21 91MB self-installing executable. Last revised/verified: 2013-03-04Select Java SE 7u21 JDK then your platform W2K/XP/W2003/Vista/W2008/W7-32/W7-64/W8-32/W8-64/Linux/LinuxARM/LinuxX86/LinuxX64/Ubuntu/Solaris/SolarisSPARC/SolarisSPARC64/SolarisX86/SolarisX64/OSX and choose Windows (or whatever your platform). Note that Apple Mac OSX is now included. You don’t have to put up with a severely out of date version from Apple any more. For W7-64/W8-64, you will need both 64-bit JDK for the desktop and a 32-bit JRE for 32-bit browsers.) If both browsers don’t show up in the Java control panel, manually add the missing one. If you have a 64-bit browser, you can run your Applets and Web starts in 64-bit too. All the common Windows browsers are still 32-bit. The version you most likely want to download is: jdk-7u21-windows-i586.exe or possibly: jdk-7u21-windows-x64.exe for 64-bit Windows 7. JavaDB/Derby is supposed to be included in the JDK. After the install, make sure the Java DB SQL (Standard Query Language) engine install worked by running J:\Program Files\Java\jdk1.7.0_21\db\bin\sysinfo.bat and checking that it is the expected Java DB version. The JDK, described here, is for people who want to write their own Java programs. If all you want to do is run them, or browse Applets on the web, you should use the much smaller JRE instead. You don’t need both. The JDK includes the JRE. The Oracle installer is badly designed. Watch out for the following: There are two JREs (Java Runtime Environments). The installer asks you about the one embedded in the JDK, and only at the last minute asks you about the separate one usually installed on C:. The installer won’t automatically set up the PATH and JAVA_HOME environment variables for you. The installer won’t automatically set up the associations for *.jar and *.jnlp for you.	download documentation download API (Application Programming Interface) documentation. jdk-7u21-apidocs.zip 58MB in zipped HTML (Hypertext Markup Language) format. It has changed since the previous version, so you can’t just drag over your old docs directory. It is not at the top as advertised. Look about ¾ down the page. The link in is the middle of the page after the JDK and JRE downloads before the source downloads. It is confusing because there is a section of miscellaneous documentation at the top, which does not include the API documentation. You just unzip the download into your J:\Program Files\java\jdk1.7.0_21 directory with folder names. There is no installer. I suggest you mark the docs directory as compressed to save space after you download and unzip it. Only the very curious will want the source downloads. If you selected the default C: location, it will install a JDK in: C:\Program Files\java\jdk1.7.0_21 and a client JRE in: C:\Program Files\java\jre7 . If you manually selected a location, then the JDK will be where you specified e.g. A 64-bit JDK in J:\Program Files\java\jdk1.7.0_21 or a 32-bit JDK in J:\Program Files (x86) \java\jdk1.7.0_21 for a 32-bit Java on 64-bit Windows 7. You need to download and put the documentation in: J:\Program Files\java\jdk1.7.0_21 \docs After you have installed the documentation, build a bookmark to it in your browser	release notes. To use any of the  rem compiling with JDK 1.7 features turned on javac.exe -source 1.7 -target 1.7 MyProg.java rem -30- You might consider renaming src.zip to src.jar so that your IDE can see the source files for cross referencing. The install also puts some files in C:\Program Files\java\common files. It will install two copies of the JRE, a private one with debugging turned on in J:\Program Files\java\jdk1.7.0_21 \jre for the SDK tools, and a public one with debugging turned off in C:\Program Files\java\jre7 for all apps to use. The private debugging version is designed for tracing code through step by step. JET (Just Enough Time) Version 8.0 supports up to Java 1.6.0_43. (The most recent Oracle release is 1.7.0_21 ), currently one full version behind. You can use the 1.7.0_21 compiler, but you must use -target 1.6. Even if you avoid the new 7.0 features JET cannot handle code compiled with -target 1.7. Last revised/verified: 2013-04-19. JET supports XP/W2003/Vista/W2008/W7-32/W7-64/Linux JET comes with a precompiled JRE, so you don’t actually need to install a Oracle JRE 1.6.0_43 though obviously you will need some JDK for development, usually JDK 1.7.0_21. JET 8.0 now lets you natively compile Tomcat and Tomcat applications. Support for JDK 1.7.0_21 has been delayed to expedite release of 64-bit JET. There are currently no MPs (Modifier Packs) to download and install for Jet 8.0.
JDK 1.6.0_45 (obsolete)	JDK 6 Update 43 67.42MB self-installing executable. Select JDK 6 Update 45 then your platform and choose Windows (or whatever your platform. Windows 7 64-bit, you will need both 64-bit JDK for the desktop and a 32-bit JRE for 32-bit browsers.) If both browsers don’t show up in the Java control panel, manually add the missing one. If you have a 64-bit browser, you can run your Applets and Web starts in 64-bit too. All the common Windows browsers are still 32-bit. The version you most likely want to download is: jdk-6u45-windows-i586.exe or possibly: jdk-6u45-windows-x64.exe for 64-bit Windows 7. The JDK, described here, is for people who want to write their own Java programs. If all you want to do is run them, or browse Applets on the web, you should use the much smaller JRE instead. You don’t need both. The JDK includes the JRE. The Oracle installer is badly designed. Watch out for the following: You must set the drive of the JDK and Derby SQL separately. You must click the various options to access the boxes to fill in the install directories. (Oracle may have stopped bundling Derby, though they claim they do, or just not mentioning it if it is already installed.) There are two JREs. The installer asks you about the one embedded in the JDK, and only at the last minute asks you about the separate one usually installed on C:. The installer won’t automatically set up the PATH and JAVA_HOME environment variables for you. The installer won’t automatically set up the associations for *.jar and *.jnlp for you.	download documentation Downloadable documentation. Online documentation. You will have to use the online docs or the Java 1.7 docs. Only the very curious want the source downloads. It will install a JDK in: J:\Program Files\java\jdk1.6.0_45 and a client JRE in: C:\Program Files\java\jre7 or J:\Program Files (x86) \java\jdk1.6.0_45 for a 32-bit Java on 64-bit Windows 6. and a debugging/server JRE in: J:\Program Files\java\jdk1.6.0_45\jre. The documentation goes in: J:\Program Files\java\jdk1.6.0_45\docs After you have installed the documentation, build a bookmark to it in your browser:	release notes. To use any of the  rem compiling with JDK 1.6 features turned on javac.exe -source 1.6 -target 1.6 MyProg.java rem -30- You might consider renaming src.zip to src.jar so that your IDE can see the source files for cross referencing. New features in Java version 1.6: Nimbus look and feel various features for quicker starting, which are disabled in Vista. hardware accelerated video more ability to configure Applets The install also puts some files in C:\Program Files\java\common files. It will install two copies of the JRE, a private one with debugging turned on in J:\Program Files\java\jdk1.6.0_45\jre for the SDK tools, and a public one with debugging turned off in C:\Program Files\java\jre6 for all apps to use. The private debugging version is designed for tracing code through step by step. You can also download source the source for everything. You don’t need it other than for curiosity. JET Version 8.0 supports up to Java 1.6.0_43. (The most recent Oracle release is 1.7.0_21 ), currently one full version behind. You can use the 1.7.0_21 compiler, but you must use -target 1.6. Even if you avoid the new 7.0 features JET cannot handle code compiled with -target 1.7. Last revised/verified: 2013-04-19. JET supports XP/W2003/Vista/W2008/W7-32/W7-64/Linux JET comes with a precompiled JRE, so you don’t actually need to install a Oracle JRE 1.6.0_43 though obviously you will need some JDK for development, usually JDK 1.7.0_21. JET 8.0 now lets you natively compile Tomcat and Tomcat applications. Support for JDK 1.7.0_21 has been delayed to expedite release of 64-bit JET. There are currently no MPs to download and install for Jet 8.0.
JDK 1.5.0_22 (obsolete)	download JDK. The Windows Installation version is 88MB and contains NetBeans. If you don’t want NetBeans, look lower on the page under 32-bit/64-bit for Windows/Linux/Solaris SPARC 32-bit for Solaris x86 where you can get the vanilla 55MB JDK. You then get a choice of online or offline install. offline is preferable since it lets you reinstall later even if you have no Internet access or if Oracle stops making it available. online uses less disk space since it downloads as needed during the install. You can also put the offline version on CD (Compact Disk) for backup or to pass on to others. JDK version 1.5 is slated for end of life 2009-10-30, last updated on 2009-11-03. The JDK includes source in src.zip and class files in jre\lib\rt.jar. Includes the JRE and Java Web Start runtime jawaws.exe. Does not include JavaMail or JAF (Java Activation Framework).	download documentation Download documentation. 49MB in zipped HTML format. The link is way at the bottom of the page after the JDK executable downloads. I suggest you mark the docs directory as compressed to save space after you download and unzip it. Oracle’s older Java 1.5 documentation on : online documentation for JDK 1.5 .	You might consider renaming src.zip to src.jar so that your IDE can see the source files for cross referencing. This release includes major changes to the Java language such as boxing/unboxing (automatic int <-> Integer conversion), generic (Collections know what sort of objects are in them), enhanced for loops for iterating over Collections, and typesafe enumerations, and variable numbers of argument to a method. Here is a summary of the changes
JDK 1.7.0_40 (beta)	download executables. Last revised/verified: 2013-05-07	download documentation. Download production documentation.	The main reason to use a beta version is to find and report bugs.
JDK 1.8 (beta)	This version supports lambda expressions.	Docs on Lambda Expressions

Polishing and Testing The JDK Install

1. Click start ⇒ Control Panel ⇒ Java. Make sure all your JREs/JDKs are registered there. If not ask it to find and register them. Remove any JREs/JDKs you are not using.
2. Configure your set environment for the CLASSPATH. If you are not sure use CLASSPATH=. See environment for details of how. See classpath for details.
3. Configure environment variable JAVA_HOME=J:\Program Files\java\jdk1.7.0_21 to point to the JDK.
4. Configure environment variable PATH to include the JDK binaries directory J:\Program Files\java\jdk1.7.0_21 /bin This ensures that javac.exe is on the path. See path for details.
5. Set your JAVA_HOME environment variable to the JDK directory e.g. J:\Program Files\java\jdk1.7.0_21. Some software such as Caucho Resin finds Java using this variable rather than poking around in the registry. See environment for details on how to set it.
6. Install unlimited strength encryption per these instructions.
7. Configure *.jar files to be executable and clickable, so you can run them just by typing their names on the command line or double clicking them in the explorer. See making jar files executable and double clickable for details on how to set up the necessary association.
8. Copy your various library jars into the J:\Program Files\java\jdk1.7.0_21 \jre\lib\ext directory.

   Sooner or later you will have to reinstall the JDK/JRE and you will lose your ext directories. You can quickly rebuild them if you maintain a bat file like this and run it after every JRE/JDK install. Adjust the file to account for where your ext dirs are and where the jars are you need.
9. Set up your J: drive to point to the drive where you installed the JDK. For detailed instructions see J: drive.
10. The JDK contains a JRE. Test the JRE the same way you would had you downloaded a standalone JRE.
11. Type java.exe -version. You should see Java version 1.7.0_21.
12. Type javac.exe -version. You should see javac 1.7.0_21.
13. Compile and run a HelloWorld application.
14. Fix any bookmarks in your browser into the JDK locally or at Oracle.
15. If you can’t get it to work, follow the failed install instructions.

Installing under Linux

To access the JDK under Linux, you need to set up two environment variables JAVA_HOME and the PATH.

Contents of The JDK

• In the J:\Program Files\java\jdk1.7.0_21 directory you will find src.zip/ src.jar which contains the source to the Java core libraries.
• In the J:\Program Files\java\jdk1.7.0_21 \bin directory you will find javac.exe, java.exe, javaw.exe, javaws.exe and javadoc.exe. and other utilities like: keytool.exe pack200.exe policytool.exe and unpack200.exe.
• In the J:\Program Files\java\jdk1.7.0_21 \lib directory you will find the jar files, especially dt.jar/ rt.jar/ classes.zip which contains most of the Java core library class files. Oracle likes to rename this file frequently.
• In the J:\Program Files\java\jdk1.7.0_21 \jre\bin directory is a duplicate of the crucial J:\Program Files\java\jdk1.7.0_21 \bin files that are also distributed separately bundled in the JRE, e.g. java.exe, javaw.exe, javaws.exe, keytool.exe pack200.exe policytool.exe and unpack200.exe. but not the developer tools such as javac.exe or javadoc.exe including Java Web Start. In jre\lib\ext you can put jars you want automatically included on the path.
• In C:\Program Files\java\jre7 \bin is yet a third copy of the crucial files, a duplicate of the JRE, including java.exe, javaw.exe, javaws.exe, keytool.exe pack200.exe policytool.exe and unpack200.exe. but not the developer tools such as javac.exe or javadoc.exe

Why Three Copies of the Executables?

1. The C:\Program Files\java\jre7 \bin version is for ordinary production client use.
2. The J:\Program Files\java\jdk1.7.0_21 \jre\bin version is for production servers. The java.exe there understands the -server option.
3. The J:\Program Files\java\jdk1.7.0_21 \bin version is for debugging.

For client use, you don’t need to put anything on the path. The JRE installer puts a dummy copy of java.exe on the path in C:\WINNT\system32 to get things started. When it is invoked, it looks in the registry to find the current actual java.exe. javaws.exe works the same way.

Caveats

• Oracle downloads often fail because they give them the non-standard MIME (Multipurpose Internet Mail Extensions) type of magnus-internal/cgi. Set your browser to treat this MIME type just like application/octet-stream to simply download the files.
• Note, Oracle’s install instructions for the older releases may tell you to hit download software. There is no such button. Hit continue instead. The JDK package optionally upgrades your Winsock. Undo with C:\WINDOWS\WS2BACKUP\WS2BACKUP.BAT or remove/reinstall Win95 dialup networking. The new socket software did not work for me and for a few other people I talked to. Plan your recovery before you install. Without a working Winsock you won’t be able to ask for help or go searching the net for a solution.
• JDKs (Java Development Kits) sometimes don’t include the javax packages (except for Swing). You must download those separately. I have provided additional help finding jars, namely where to download additional jars.

Failed Installs

1. Check that the JDK/JRE download is the expected size. The download may have aborted.
2. For Java Applets to work in a browser, there must be a copy of msvcr71.dll in the C:\windows\system32 folder. If there isn’t, copy it from C:\Program Files\java\jre7 \bin.
3. Make sure that the anti-spyware program Webroot SpySweeper, is turned off. It will interfere with installs.
4. Make sure no copies of any of the Java utilities are running. Use the task manager to kill any that won’t quit normally.
5. Uninstall all Java JDKs and JREs with Start ⇒ Settings Control Panel ⇒ add/remove programs.
6. Reboot.
7. Manually delete any remaining files in the C:\Program Files\java\jre7 , J:\Program Files\java\jdk1.7.0_21 and C:\Users\userid\AppData\LocalLow\Sun directories. Make sure there are no copies of java.exe, jawaws.exe, jawaw.exe or javac.exe anywhere on your machine including C:\Windows\System32.
8. Manually delete any *.msi files for Java buried in the C:\Windows tree. Click search ⇒ Files and Folders ⇒ *.msi to track them down.
9. Go into the registry with regedit.exe and delete all reference to the Java installation i.e. HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft. If you are not sure, leave the entry alone.
10. Delete all the files in C:\Documents and Settings\userId\Application Data\Sun\Java or your equivalent, such as C:\Users\userId\AppData\LocalLow\Sun, C:\Users\userId\AppData\Roaming\Sun and C:\Windows\Sun. You might have to reboot to free locks to let you kill the directories.
11. Run a registry cleaner such as Ace to get rid of any registry references to the deleted files.
12. Reboot.
13. Reinstall, including setting up the set JAVA_HOME, set CLASSPATH, set PATH environment, and the ext directory.
14. Sometimes uninstall, install to a different directory, uninstall, install to the original directory will clear it.
15. If Java runs standalone, but does not work in your browser, test your JRE browser hooks by running Wassup. It should tell you that your browser is using the JVM (Java Virtual Machine) version you just installed. Look for the line marked java.version. If Wassup does not run, or you have the wrong version, go into Start ⇒ Settings Control Panel ⇒ Java Plug-In ⇒ Browser and turn off each browser, then click apply, then turn them on again, then hit apply again. Then retest with Wassup.
16. Have a look at the hidden Java Web Start control file C:\Documents and Settings\administrator\Application Data\Java\Deployment\deployment.properties. Don’t edit it. If you see something wonky (e.g. references to an uninstalled JVM ), go into the Control Panel ⇒ Java Control Panel and turn things off and on again and hit apply to refresh the file. If that does not work, make a backup and try deleting the deployment.properties file, then try going into the Java Control Panel and clicking reset. The set everything up from scratch. If that does not work try editing a copy of the original deployment.properties file, sorting the entries first to make it clearer what they do, and installing it back as the official deployment.properties.

Retrofitting

1. Swing
2. IBM (International Business Machines) ’s Java version 1.2 security classes.
3. Collection classes (except the natural order stuff).
4. Help engine.

JDK Differences

Upgrading Your JDK to a New Version

1. Download and install the new JDK.
2. Check your set environment for outdated references, e.g. JAVA_HOME, classpath, path.
3. Update any *.bat files that point to the old JDK/JRE to point them to the new JDK/JRE.
4. Copy your various auxiliary jars into the ext directory. See ext directory for details.
5. Reconfigure the compiler used in your various IDE project settings, update library includes, e.g. tools.jar and recompile everything.
6. Move the doc documentation from your old JDK to the new one
7. Check that the association for *.jnlp is set up to point to the new javaws.exe in both Windows and your browser. See installing Java Web Start for details.
8. If you use SlickEdit, copy src.zip to scr.jar and reindex it.
9. If that does not work, uninstall all JDKs and JREs. Then manually remove any vestigial directories. And start over.
10. If that does not work, clean out the Java registry entries and all the JDKs and JREs and start over. Closures, pauseless garbage collection.

Here is what I do when Oracle releases a new version of the JDK. For you, it is simpler:

1. Notice update in Vercheck and configure new Vercheck version.
2. Tell everyone on com.lang.java.programmer about the new version.
3. Download and install the 64-bit JDK and 32-bit JRE.
4. Download and install Java docs.
5. Adjust and run search/replace script to update version 6 and 7 version numbers in all bat, java, html, xml, jnlp etc. files.
6. Adjust fixext.btm and run it to build environment sets and construct ext libraries.
7. Manually patch web pages about the JDK and JRE and the Java source code that records Java version into.
8. Configure IntelliJ with new JDK.
9. Tidy all source code (4-step process).
10. Rebuild, clean compile everything the new javac.exe.
11. Uninstall the old JDK and JRE. Prune the remnants.

RFE (Request For Enhancement)

• Show all installed JREs in the Java control Panel
• Do whatever it takes to make Java Applets and Java Web Start work in all installed browsers without further tweaking.