Downloading and setting up DrJava
DrJava is a free environment for writing and running Java programs. It is installed on CIT's computers throughout the campus and in the ACCEL lab.
Please note that there are two versions of Java. The older version, Java 1.4.2, and the newer version, Java 1.5. For most of the semester, it will not matter which version you are using. We will not make use of the new features in Java 1.5.
Java SE 8 Archive Downloads (JDK 8u211 and later) Go to the Oracle Java Archive page. The JDK is a development environment for building applications using the Java programming language. The JDK includes tools useful for developing and testing programs written in the Java programming language and running on the Java TM platform.
You need a Java virtual machine
Dr java Icons - Download 160 Free Dr java icons @ IconArchive. Search more than 600,000 icons for Web & Desktop here. Java 5 compatibility has been dropped. To use DrJava, you will need Java 6 or newer. New features since the last stable release: - DrJava is now compatible with Java 8 and perhaps with future editions of Java. Bug fixes since the last stable release: - DrJava correctly finds and labels Oracle JDK 7 compilers on Mac.
You will need the Java software development kit (JDK) from the Sun website. THIS MAY ALREADY BE ON YOUR COMPUTER. Don't attempt to download and install it unless you know you don't have it. If you have a Macintosh running Mac OS X, you almost certainly have it. If you have a PC, this site can check whether you have it:
If you need the Java software development kit (JDK) get it from this website:
See the Popular Downloads link on the right side of that page. Choose J2SE 5.0. Also, choose the J2SE JDK or SDK (not just the JRE and not the 'bundles' that include other programming environments, such as netBeans). Warning: this is a big download!
Can't execute jar files
If you cannot double-click on a jar file to start it running, or if you cannot execute any of the commands java, javac, javadoc, or jar, you probably have not set your path correctly. We explain this for Windows 2000; older windows systems are similar.
Your system contains a variable that lists directories with executable files in them. Type 'path' in a command-line window. The line that is printed contains path names separated by semicolons. For example, one path name may be:
C:WINNTsystem32
Free Java Download For Mac
There should be a path that looks like this: C:j2sdk1.4.1_02bin. This is a directory called bin inside the directory where you installed the sdk. It may be different on your computer. If such a path is not there, you have to add it. Bring up the help in your Windows system, open the index, and look for 'path'. There, you will find instructions on appending another directory to variable path. It may be something like this (but read the instructions):
path %path%;C:j2sdk1.4.1_02bin
Downloading DrJava
The easiest thing for you to do is to download this version of DrJava drjava-stable-20080106-0744. This version is supposed to work whether you have Java 1.4.2 or Java 1.5, and we advise using it.
If you want, open this web page (by clicking the link) in your browser and choose another version of DrJava to download. Get the latest version. Note that DrJava won't run unless you have a Java 2 v1.3 (or later) virtual machine already installed.
Warning: you may get a dialog saying something about a 'JAR archive security check'. If you do, just right-click on the DrJava download link and select 'Save Link As' (or the equivalent in your browser).
We know that all this setup can be annoying, but you have to do it only once!
A common DrJava problem: finding tools.jar
Question: I downloaded Sun's J2SE SDK and DrJava. When it came to actually running DrJava, the following window kept popping up even though somehow DrJava still managed to run without me finding the file --what should I do?:
Compiler not found. The file you chose did not appear to contain the compiler. Would you like to pick again? The compiler is generally located in 'tools.jar', in 'lib' subdirectory under your JDK installation director. (If you say 'No', DrJava will be unable to compile programs.)
Answer: First, make sure you installed the Java SDK, not the JRE. (See above.)
Next, file tool.jar comes with the JDK. The usual location is
C:Program FilesJavajdk1.5.0_02libtools.jar
if you have followed the default options during the JDK download process. You can also use a desktop tool to search for this file on your computer. You simply need to set DrJava's Preferences to the correct path. To do so, follow these menu items: Edit - Preferences - Resource Locations - Tools.jar Location then type or browse to the correct location.
Running DrJava
There are several ways to run DrJava:
- From the command line, you can type java -jar drjava-stable-20061025-1556.jar
- On many platforms, you can simply double-click the jar file to start DrJava.
- On OS X, you can download the drjava-stable-20061025-1556.jar-osx.tar.gz package. You can then run DrJava as a normal application.
Documentation --how to use DrJava
The demos given in class and in the demo sessions should help, if you take notes. However, here is documention on using DrJava (http://drjava.sourceforge.net/userdocs/) on the web.
Wrong-version error.
Do you get a message that looks like this?
Error: cannot access javax.swing.JFrame
bad class file: C:Program FilesJavajre1.5.0librt.jar(javax/swing/JFrame.class)
class file has wrong version 49.0, should be 48.0
Please remove or make sure it appears in the correct subdirectory of the classpath.
It may mean that your computer has two different systems on it and is an inconsistent state. If your computer has jre5.0, then it cannot use SDK 4.7. Uninstall SDK4.7 and download JDK 5.0 and use its tools.jar.
Last updated: October 10, 2018
You can find Java version on Mac without running a Java applet in your web browser. Fortunately, there are a variety of methods to find the Java version on Mac. Below is a description of some of those methods. Also see Java Support in Safari 12.
Using Command Line in Terminal
Terminal is a program included with macOS that provides command line access to the operating system. Terminal is located under Applications folder -> Utilities folder. To find the Java version using command line, launch the Terminal application. Type or copy/paste the following line into the Terminal window:
/Library/Internet Plug-Ins/JavaAppletPlugin.plugin/Contents/Home/bin/java -version
The Java version will display as output in the Terminal window, and will look similar to the output below:
java version '1.8.0_40'
Java(TM) SE Runtime Environment (build 1.8.0_40-b27)
Java HotSpot(TM) 64-Bit Server VM (build 25.40-b25, mixed mode)
In this case, Java 8 Update 40 is the Java version installed on this Mac.
Using the Java Control Panel
You may find Java version on Mac using the Java Control Panel instead. For information about locating the Java Control Panel, please see the Where is the Mac Java Control Panel located article. Once you have launched the Java Control Panel, click the General tab.
In the section entitled About, click the About… button. A new About Java window will launch. Java version information will display within the window.
In this case, Java 8 Update 40 is the Java version installed on this Mac.
Using the Online Test Java Page
You may also test your Java online to determine which version of Java is installed on your Mac. To test Java on your Mac, visit the Test Java page provided by Oracle on its Java.comweb site. This utility will not only check your current Java installation, but will also remove old Java versions from your computer that may pose a security threat to your system. If your Java is working correctly, and no out-of-date Java versions are found, you will see the following notification accompanied by information about your Java installation and your computer:
As it states in the Verified Java Version web page, Java 8 Update 40 is installed on this Mac. If your Java is not working properly, the Test Java page displays additional configuration options that you may need to check, as well as download and installation instructions if needed.
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