在Linux上编译并运行HelloWorld.java

Question

I have created HelloWorld.java file in a linux folder. I would like to compile and run it. As I am doing it first time, and no such question posted here. Below is the content of Java File:

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello...How are you");
    }
}

I see Java is installed on the server. Below are commands and their output.

rakeshth@ldnserver000590 DEV $ ls
HelloWorld.java
rakeshth@ldnserver000590 DEV $ java -version
java version "1.7.0_25"
Java(TM) SE Runtime Environment (build 1.7.0_25-b15)
Java HotSpot(TM) 64-Bit Server VM (build 23.25-b01, mixed mode)
rakeshth@ldnserver000590 DEV $ javac HelloWorld.java
-bash: javac: command not found
rakeshth@ldnserver000590 DEV $ java HelloWorld.java
Error: Could not find or load main class HelloWorld.java

Please, let me know steps to compile and run this Java file.

Answer 1

-bash: javac: command not found

It seems that your javac application is not in the PATH or it's missing.

First you should try to figure out whether you have installed a JRE or a JDK in your system. Java Runtime Environment (JRE) does not have the javac command . You need to get familiar with the linux commands to find files and symbolic links. You should look for javac which should be under the JDK_installation_folder/bin ex. "/usr/local/java/jdk1.7.0_51/bin/javac"

Example:

> whereis java
java: /usr/bin/java /etc/java /usr/bin/X11/java /usr/local/java /usr/share/java
> readlink -f /usr/bin/java 
/usr/local/java/jdk1.7.0_51/jre/bin/java
> ls /usr/local/java/jdk1.7.0_51/bin/javac
/usr/local/java/jdk1.7.0_51/bin/javac

Last line proves that javac is there . If you JDK is not installed download it here . if it is you can compile your example like this example

> /usr/local/java/jdk1.7.0_51/bin/javac HelloWorld.java
> ls HelloWorld.class 
HelloWorld.class
> java HelloWorld
Hello...How are you

If you want to put your javac in the path you could create a symbolic link to it. Example:

> sudo ln -s /usr/local/java/jdk1.7.0_51/bin/javac /usr/bin/

If you want to put it in the path check out this tutorial.