Omgtrips

FIX: To use the java command-line tool you need to install a JDK (MAC OS X) Last updated on February 17th, 2018. The following pop up message is displayed randomly on a Macbook Pro: 'To use the java command line tool you need to install a JDK. Jul 11, 2015  To use the 'java' command-line tool you need to install a JDK. How to install Java JDK on Mac OS X ( with JAVA. How To Install XCode and XCode Command Line Tools on OS X Mountain Lion.

So you just upgraded your Mac (probably to Yosemite) and now you are getting annoying browser errors that say “To view this web content you need to install the Java Runtime Environment.” More annoyingly, after clicking through to Oracle’s Java.com to “Download Java for Mac OS X” and installing it, you still get the error! Here’s why, and how to fix it.

The reason that you still get the “you need to install the Java Runtime Environment” even after you have installed it from that link is because… wait for it… that is the wrong link.

You see, that error is being thrown by Oracle, and so naturally it directs you to Oracle’s Java for OS X download page.

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Where clicking “More info” on the Java Runtime Environment error takes you

BUT..you actually need the official Apple version of Java for OS X.

To get Apple’s Java for OS X, go here:

Be sure to restart your browser after installing.

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Hello, World in Java on Mac OS X

This documents instructs you on how to setup a Java programmingenvironment for your Mac OS X computer and provides a step-by-stepguide to creating, compiling, and executing a Java program.We assume you are running at least OS X 10.2.3.All of the software is freely available on the Web.

Java

You will use the Java compiler javac to compile your Java programs andthe Java interpreter java to run them.Mac OS X includes implementation of Java 2 Standard Edition (J2SE) 1.4.1,so there is nothing to do in this step.

Command line interface

You will type commands in an application called the Terminal.You might enjoy reading Neal Stephenson's light-heartedessay In the Beginningwas the Command Line.

• Open a terminal window. You can find this underGo -> Applications -> Utilities. Drag the Terminal to your dock sinceyou will be using it frequently.
• You should now have a Terminal window somewhere on the screen.It will have a command prompt that looks something like:

  To check that you have the right version of Java installed, typethe text in boldface below.

  If Java is installed, you should see something like:

  Now, check that the Java compiler is accessible.

  If it is installed, you should see something like

  If not, install the Developers Tools CD that came with your Mac anduse Software Update to make sure you have the latest version.

  Now, create a directory to store your Java programs.In the window containing the Command Prompt, type the bold commandsbelow:

  The mkdir command creates a new directory;the cd command changes the current working directory.After executing these commands, your working directoryis the newly created ~username/introcs/hello/. All of yourfiles for Assignment 0 will go here.Don't be scared by the Terminal - you will only need to use afew basic commands. Keep this window open since you will need it laterin the assignment.

  Since you will be using the Terminal frequently, we recommend customizingWe recommend customizing the default settings....

Text Editor

You will type and edit your programs in a text editor called JEdit.JEdit is similar to conventional word processors like MS Word,but it features many specialized programming tools includingsyntax highlighting, bracket matching, auto indenting, indentshifting, line numbering, and commenting out code. It's even written in Java.

• Downloadthe latest stable version of JEdit using the MacOSX package link.
• We recommend the following JEdit customizations.
  • Enable Mac OS style menubar inUtilities -> Global Options -> Plugins -> Mac OS Settings
  • Change the default indentation to four spaces viaUtilities -> Global Options -> Editing -> Indent Width andUtilities -> Global Options -> Editing -> Tab Width. Global Options -> Editing -> Soft tabs.-->
  • Change the default tab width when printing to four spaces viaUtilities -> Global Options -> Printing -> Tab width when printing
  • Add line numbers by checking Utilities -> Global Options -> Gutter -> Line Numbering
  • Allow at most 80 characters per line byUtilities -> Global Options -> Editing -> Word wrap -> hard andUtilities -> Global Options -> Editing -> Wrap margin -> 80.
  • Change the default line separator to Unix viaUtilities -> Global Options -> Loading & Saving -> Default Line Separator
  • Remove the annoying . that marks the end of a line by uncheckingUtilities -> Global Options -> Text Area -> End of Line Markers
• To associate .java files with JEdit so that when you double-click a .java file,it opens it in JEdit:
  • Right click a .java file (or click then shift-right click it if using Windows NT)
  • Choose Open With...
  • Select JEdit from the list of programs or locate JEdit by selecting Otherif necessary.
  • Check the Always use this program to open this file type box

Apple purists may prefer Project Builder which can be found in the Findervia Computer -> OS X Partition -> Developer -> Applications -> Project Builder.

Create the program

Java Command Options

Now you are ready to write your first Java program.

• Launch JEdit Start -> jEdit.
• In the JEdit window, type the Java program exactly as it appears below.If you omit even a semicolon, the program won't work.

  When you're done, save the program usingFile -> Save As, chose the directory C:introcshelloand type in the file name HelloWorld.java.The file name is case sensitive and must exactly match the name of the classin the Java program. Don't forget to include the .java extension in thefile name.

Compile the program

It is now time to convert your Java program into a form more amenable for executingon a computer.

• From the Command Prompt, type

  If javac complains in some way, you mistyped something, and you should check your program carefully. Ask for help if you can't see the mistake.

  If everything went well, you should see the followingin the Command Prompt:

  Silence is golden in computer science.

Java Command Line Arguments

Execute the program

Now it is time to run your program. This is the fun part.

• At the Command Prompt, type
• If all goes well, you should see
• You may need to repeat this edit-compile-execute cycle a few times before it all goes smoothly.Use the up and down arrow keys to repeat previous commands and avoid extra typing.

Congratulations, you are now a Java programmer!

Troubleshooting

Java Command Pattern

When I try to run java I get: Exception in thread 'main'java.lang.NoClassDefFoundErrorYour CLASSPATH may have been set by some other program so that it no longer includes the current working directory in the search path. Try running your program with the command line