JRE : Java Glossary

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jre Duke logo JRE
Introduction Linux
Which Java? Android
Downloading the JRE Multiple JREs
Testing Your JRE JDK
Silent JRE Installs Links

Introduction

JRE (Java Runtime Environment). This is the subset of Oracle’s JDK (Java Development Kit) that you can ship with your application. It is free.
The JRE, described here, is for people who just want to run Java programs or browse Applets on the web. You must use the much larger JDK if you want to write your own Java programs. You don’t need both.

To use the JRE you must be running W2K, XP, W2003, Vista, W2008, W7-32, W7-64, W8-32, W8-64, W2012, Linux, LinuxARM, LinuxX86, LinuxX64, Ubuntu, Solaris, SolarisSPARC, SolarisSPARC64, SolarisX86, SolarisX64 and OSX or Solaris.

Which Java.exe?

When you install multiple JREs (Java Runtime Environments)and JDKs (Java Development Kits) you will have many different java.exe, javaw.exe, javaws.exe and javac.exe installed. Which one is used depends on which JREs and JDKs you have installed, which JVMs are enabled in the Java Control Panel, the SET JAVA_HOME, the path, the current directory and the phases of moon used in a pseudo random number generator to select one of the installed Javas. Verify you are using what you expect with java.exe -version.

If you install more than one JRE/JDK, you can select the java.exe you want with:
"C:\Program Files (x86)\Java\jre8\bin\java.exe" -version
Test with -version. Just going to the directory and typing java.exe will not necessarily work.

Downloading the JRE

You can find the various downloads with your browser. For Vista, W2008, W7-32, W7-64, W8-32 and W8-64, make sure you are logged in as an administrator before you install. Some suggest it is best also to turn on UAC (User Account Control) (that irritating Visa User Account control) during the install. The downloads are labelled as updates, but they are complete in themselves. You don’t need to install a previous version.

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).

A static JRE is one kept on an old version without upgrading it to test software on old the old version.

Version Executables Notes
JRE  1.8.0_25
(current)

Download 20MB self-installing executable. Look for the third entry, Java JRE 8 Then click Download. Then select your platform tick the licence agreement and Click Windows Offline Installation. This is most likely the version you want to download. For W2K, XP, W2003, Vista, W2008, W7-32, W7-64, W8-32, W8-64, W2012, Linux, LinuxARM, LinuxX86, LinuxX64, Ubuntu, Solaris, SolarisSPARC, SolarisSPARC64, SolarisX86, SolarisX64 and OSX, make sure you are logged in as an administrator before you install. The install will work more smoothly if you launch the install of the download with run as administrator and if you have UAC turned on. Even if you have 64-bit Windows 7, you probably still want the 32-bit Windows version, since that is what most browsers require. You might want the 32-bit version for Applets and Java Web Start and the 64-bit version for desktop applications.

The download includes the Java Plug-in for Applets and Java Web Start. It includes the JVM (Java Virtual Machine) and the standard class library files, but no source, and no javac.exe. It does not include JavaMail or JAF. It will install in C:\Program Files\java\jre1.8.0_25\ . If you want to write your own Java programs, install the JDK instead.
JRE  1.7.0_72
(old)

Download 20MB self-installing executable. Look for the sixth entry, Java JRE 7u72 Then click Download. Then select your platform tick the licence agreement and Click Windows Offline Installation. This is most likely the version you want to download. For W2K, XP, W2003, Vista, W2008, W7-32, W7-64, W8-32, W8-64, W2012, Linux, LinuxARM, LinuxX86, LinuxX64, Ubuntu, Solaris, SolarisSPARC, SolarisSPARC64, SolarisX86, SolarisX64 and OSX, make sure you are logged in as an administrator before you install. The install will work more smoothly if you launch the install of the download with run as administrator and if you have UAC turned on. Even if you have 64-bit Windows 7, you probably still want the 32-bit Windows version, since that is what most browsers require. You might want the 32-bit version for Applets and Java Web Start and the 64-bit version for desktop applications.

The download includes the Java Plug-in for Applets and Java Web Start. It includes the JVM and the standard class library files, but no source, and no javac.exe. It does not include JavaMail or JAF. It will install in C:\Program Files\java\jre7. If you want to write your own Java programs, install the JDK instead.
any older JRE In the you can find nearly every JRE Oracle ever released, using a fill in the blanks description of what you want. If you get a broken link try composing the URL (Uniform Resource Locator) from this pattern: http://java.sun.com/products/archive/j2se/5.0_22/index.html

You might want to manually set your JAVA_HOME environment variable to the JRE directory e.g. C:\Program Files\java\jre1.8.0_25\ . Some software finds Java using this variable rather than poking around in the registry.

Polishing and Testing Your JRE

Testing your JRE is more complicated that you might expect. You want to find out if Java is working properly on the desktop, and in each of your browsers. Further, you want to test that Java Web Start is working properly on the desktop, and in each of your browsers. Just because Java/Java Web Start works in one browser, does not mean it will automatically work in another.

  1. Click startControl PanelJava. 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. Copy your various library jars into the C:\Program Files\java\jre1.8.0_25\ \lib\ext directory.

    If you have Windows 7 64-bit, you will need to install two JRE s, a 64-bit one in C:\Program Files\java\jre7 for used by your desktop apps and by your 64-bit browsers and a 32-bit one in C:\Program Files (x86)\java\jre7 for use by your 32-bit browsers.

    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.

  4. In Internet Explorer, go into Tools ⇒ Internet option ⇒ Advanced ⇒ Java(Oracle). Make sure Oracle Java is checked.
  5. In Internet Explorer, make sure all three boxes under Tools Internet option ⇒ Advanced ⇒ Microsoft VM are checked.
  6. In Internet Explorer 7+, you must OK allow blocked content permission to run Active X on the site, (even your own when running offline). This also gives permission to run Java. Since Java is perfectly safe because it runs it a sandbox, logically it should not need special permission. This roadblock to Java is just part of Microsoft’s war on Oracle and Java.
  7. Test 
    java.exe -version
    You should see the expected version you just installed, probably  1.8.0_25. It can be problematic to have more than one version installed at a time.
  8. Run Oracle’s formal Applet test of the Java JRE in a browser.
  9. Test your JRE browser’s ability to run signed Applets by running Wassup.

    It should tell you that your browser is using the JVM version you just installed, probably 1.8.0_25. Look for the line marked java.version. If Wassup does not run, or you have the wrong version, go into 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. If that still does not work, turn on the Java console, try Wassup again and look for clues.

  10. Test Java Web Start on the desktop by typing javaws.exe and running any sample application.
  11. Check that the associations for the *.jnlp extension is set to point to the appropriate javaws.exe and *.jar is set to point to javaw.exe.
    The associations for *.jar and *.jnlp are fragile. They mysteriously change to obsolete versions, or javaw.exe version without a console or even unrelated programs like Winzip.exe. Using the java.exe -jar myjar.jar syntax in your bat/btm files rather is more robust than myjar.jar. It works even when the associations are corrupted.
    Confirm this in any My Computer directory display with tools ⇒ folder options ⇒ file types.
  12. Set up associations for *.jar files to make them double clickable, following the instructions here. By default the association will be set up to javaw.exe and you won’t see any output.
  13. Check that Java Web Start is working in each browser by testing SetClock. Click SetClock to test.
  14. Check the Opera browser’s quick preferences to make sure you have Java enabled. Turn on the console with tools ⇒ advanced ⇒ Java console to get some hints why it may not be working. Make sure Opera has *.jnlp files associated with mime type application-x-java-jnlp-file in preferences ⇒ files.
  15. If you can’t get it to work, follow the failed install instructions.

Silent JRE Installs

If you want to install the JRE on many machines, or an install triggered by an utter novice, you would prefer a command-line style install that did not ask any questions as it progressed. That is called a silent install. It does not mean stealthily installing the JRE or other app on a machine without the owner’s notice.

Learning More

Linux

Installing a JRE under Linux is much more complicated that under Windows. You need to perform half a dozen manual installation steps. You also need to set up a soft link from each of your browser plug-ins to the corresponding Java *.so libraries. Download and study the install instructions. You will never guess them. Consult your browser for documentation on the soft links.

Android

There is no JRE for Android. If you want to run Java ME applications on Android, you need to convert your jars to the format that Android understands. For that purpose you can use a tool such as Java/J2ME Runner.

Multiple JRE s

If you want to install multiple JRE s, first uninstall all your JDKs and JRE s, then install the JREs and JDKs the oldest version first and install them in order. If you want the JDK, there in no need to install the corresponding JRE as well.

Then instead of saying java.exe, use the fully qualified name to select which version of the java run time you want e.g. C:\Program Files\java\jre1.8.0_25\ \bin\java.exe.


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