trying to compile a java program in terminal

Question

I'm just trying to compile a simple hello world file via the terminal. Here's the code for Hello.java:

package Hello;
public class Hello {
    public static void main(String[] args) {        
        System.out.println("Hello, world!");
    }
}

this is saved in another folder, so in terminal I typed:

cd code/repositories/java to navigate to the correct directory (where I saved Hello.java) I next typed javac Hello.java and hit return. It compiled without any errors. I then tried to open the file with java Hello and it threw the following exception:

 Exception in thread "main" java.lang.NoClassDefFoundError: Hello (wrong name: Hello/Hello)
   at java.lang.ClassLoader.defineClass1(Native Method)
   at java.lang.ClassLoader.defineClassCond(ClassLoader.java:631)
   at java.lang.ClassLoader.defineClass(ClassLoader.java:615)
   at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
   at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
   at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
   at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
   at java.security.AccessController.doPrivileged(Native Method)
   at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
   at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
   at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
   at java.lang.ClassLoader.loadClass(ClassLoader.java:247

How/why does this happen and how do I go about fixing it?

You need to run the `java` command from the classpath installation directory (up one level) — Kon, Aug 21 '13 at 01:07
I also had a second problem (I had to remove `package hello;`), hence "trying to compile a java program in terminal"—terminal wasn't the only problem. The java part was also wrong, so idk if it's an exact duplicate... — royhowie, Aug 21 '13 at 01:46

dkatzel · Accepted Answer · 2013-08-21T01:33:54.273

6

The package is called Hello which makes the full qualified name Hello.Hello which means you need to have your Hello.java file in code/repositories/java/Hello

then cd to the code/repositories/java folder and call javac javac Hello/Hello.java then you can run it java Hello.Hello

On a different note, Java standard naming conventions recommend package names use lowercase letters so consider changing the package to "hello"

edited Aug 21 '13 at 01:33

answered Aug 21 '13 at 01:13

dkatzel

31,188
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yeah, I realized the lowercase name thing (already changed it to `package hello;`) – royhowie Aug 21 '13 at 01:15
the folder must match the case of the package so if the package is now "hello" then that's what the folder should be called as well – dkatzel Aug 21 '13 at 01:16
+1 but you need to compile as `javac Hello/Hello.java`. – Ravi K Thapliyal Aug 21 '13 at 01:31
Oh you're right. Fixed typo. Thanks! – dkatzel Aug 21 '13 at 01:34

score 2 · Answer 2 · answered Aug 21 '13 at 01:13

2

Remove line package Hello;. Compile and run.

answered Aug 21 '13 at 01:13

Pawel

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awesome, it worked! This was originally written in Netbeans, so I understand the difference (it's just a file without said `Hello` container folder). – royhowie Aug 21 '13 at 01:18
I had the same problem. I also coppied the code from NetBeans. – Pawel Aug 21 '13 at 01:19

trying to compile a java program in terminal

2 Answers2