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Thread: Main Class not loading

  1. #1
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    Default Main Class not loading

    Hey guys, literally just started trying to learn Java and already running into trouble-
    Version Info-
    C:\Program Files (x86)\Java\jre7\bin>java -version
    java version "1.7.0_21"
    Java(TM) SE Runtime Environment (build 1.7.0_21-b11)
    Java HotSpot(TM) Client VM (build 23.21-b01, mixed mode, sharing)

    Just trying a little 'Hello World' and I keep getting this error: "Error: Could not find or load main class C:\Java\hello2.java"

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


  2. #2
    Super Moderator pbrockway2's Avatar
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    Default Re: Main Class not loading

    A class like Hello that is designed to be "run" with a main() is normally made public. Ie, is declared as "public class Hello { etc".

    More importantly it must in a file Hello.java. The file name and class name must match: this is part of Java's way of identifying classes at runtime.

  3. #3
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    Default Re: Main Class not loading

    Still the same:

    C:\Program Files (x86)\Java\jre7\bin>java C:\Java\Hello.java
    Error: Could not find or load main class C:\Java\Hello.java

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

  4. #4
    Super Moderator pbrockway2's Avatar
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    Default Re: Main Class not loading

    You have to first compile, then run. The compiler executable is javac.exe: it turns your .java file into a binary class file. Then you use the java.exe executable to actually run the file.

    The commands are

    javac -cp . Hello.java
    java -cp . Hello

    Notice how javac expects the name of a file (to compile) while java expects the name of a class (with no extension, to run).

    The dash-c-p-space-dot business is a common way of specifying the classpath. The classpath is the place Java expects to find class files.

    ---

    Step by step instructions for compiling and running a hello world program can be found in the "Hello World!" for Microsoft Windows page of Oracle's Tutorial.

  5. The Following User Says Thank You to pbrockway2 For This Useful Post:

    3therk1ll (June 7th, 2013)

  6. #5
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    Default Re: Main Class not loading

    Got it now, I had the wrong version or type of Java installed *facepalm*, thanks mate.

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