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How can I compile a .java file. What programs will I need and if I need java jdk I need help installing that. I'm very new to ubuntu so any program I need to install I will need a tutorial on how to install them.

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5 Answers 5

up vote 9 down vote accepted

To compile the file, open your terminal and type

javac filename.java

To run the generated class file, use

java filename

But to do this you need to have the Java JDK installed in your computer. You can install it with the instructions in How do I install Java?.

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OpenJDK work best for me. It's simple and I have never face any problem. Just follow these simple steps:

  1. From Terminal install the open jdk

    sudo apt-get install openjdk-7-jdk
    
  2. Write program and save the file as filename.java

  3. Now to compile use this command from the terminal

    javac filename.java
    

    If everything work well you will notice a filename.class file is also created.

  4. To run your program you compiled use the below code in terminal:

    java filename
    

NOTE

You can use any text editor (like gedit) ,

replace the filename with watever name you want

you need to be on same directory as the "present working directory" (got by running pwd) while running the command from terminal.

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You need to install a JDK, Java Development Kit. Ubuntu contains a metapackage default-jdk, which depends on currently prefered JDK. Now it is openjdk-6-jdk.

To compile a Java file to runnable .class file you can run

javac filename.java

and run it

java file

It is the most simple use-case and mostly it doesn't work because java classes mostly depends on other java classes placed in libraries.

So you would probably like to use some more sophisticated solutions. Most text editors supports Java syntax highlighting, for example jEdit, kate or vim, but they don't solve your compilation issue.

You have another option - you can install a full featured Java IDE. Ubuntu comes with both main OpenSource Java IDEs - NetBeans and Eclipse.

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For a first installation, default-jdk is a must and openjdk-X-jdk is not enough. –  JohnRos Feb 15 at 22:35

just type sudo apt-get install openjdk-6-jdk for a quick installation for java6, then you can play games with java :-)

for more detailed official documentation, please visit the link as following, http://docs.oracle.com/javase/tutorial/getStarted/cupojava/unix.html

In addition, there are millions of how-to tutorials if you head to google.com

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2  
I'd suggest that people starting to learn Java now would be best off learning the latest version, Java 7 (sudo apt-get install openjdk-7-jdk). Also, it's best to run sudo apt-get update before installing packages from the Terminal. –  Eliah Kagan Jun 3 '12 at 3:56
    
7 is only present in 12.04. 6 makes the answer more generic –  Thorbjørn Ravn Andersen Jun 3 '12 at 6:39

If for example your file is my_file.java:

class MyClass
{
    public static void main(String[] args)
     {
       System.out.println("Hello World");
     }
}

You want to do:

javac my_file.java

and then

java MyClass # The name of the class, not file

However, it is a common convention to give classes and files the same name.

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Thanks a lot it worked –  MaheshK Apr 10 at 6:57

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