即使在同一目录中的所有类之后，线程“ main”中的异常java.lang.NoClassDefFoundError：EightPuzzle错误的名称

Question

I am trying to run a class that is going to use two classes which are in the same package and directory as follows: I am using jdk 1.7 and JAVA_HOME is also set.

package cs.ai.assignment1;
/* class to be used in EightPuzzle*/
import java.util.*;
public class H1 {
    int solve(int a[][]) {
        return 1;
    }
}


package cs.ai.assignment1;

/* EightPuzzle class to store problem to be solved*/

import java.util.*;
import mtech.cs.ai.assignment1.*;
public class EightPuzzle {

    int tiles[][];

    EightPuzzle() {
        // tiles is initilized to 0 here
    }

    void input() {
        //input is taken from user and stored in tiles
    }

    public static void main(String[] args) {
        int opt = 0;
        Scanner in = new Scanner(System.in);
        EightPuzzle puzzle = new EightPuzzle();
        do {
            System.out.println("**************Welcome to 8Puzzle Game****************\n");
            System.out.println("\nChoose Heuristic Function to use");
            System.out.println("\n1. #Displaced Tiles");
            System.out.println("\n2. Manhattan Distance");
            System.out.println("\nOption: ");
            opt = in.nextInt();
            if (opt == 2 || opt == 1) {
                puzzle.input();
                break;
            }
        } while (true);
        int steps = 0;
        H1 h1 = new H1();
        H2 h2 = new H2();
        switch (opt) {
            case 1:
                steps = h1.solve(puzzle.tiles);
                break;
            case 2:
                steps = h2.solve(puzzle.tiles); // To solve the puzzle
                break;
            default:
                break;
        };
        System.out.println("\n\nThe goal was reached in " + steps + " steps");
    }
}

All these classes are in the same directory and package. They got compiled too using,

C700-Notebook-PC:~/aiAssgnmt$ javac -d . EightPuzzle.java H1.java H2.java

But, when I am trying to run them I am getting following error,

C700-Notebook-PC:~/aiAssgnmt$ java EightPuzzle.java
Error: Could not find or load main class EightPuzzle.java

So, I tried putting them all in jdk/bin and the compiled, but then I got this error,

ambarish@ambarish-Compaq-Presario-C700-Notebook-PC:~/Softwares/jdk1.7.0_25/bin$ java EightPuzzle
Exception in thread "main" java.lang.NoClassDefFoundError: EightPuzzle (wrong name: mtech/cs/ai/assignment1/EightPuzzle)
            at java.lang.ClassLoader.defineClass1(Native Method)
            at java.lang.ClassLoader.defineClass(ClassLoader.java:792)
            at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
            at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
            at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
            at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
            at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
            at java.security.AccessController.doPrivileged(Native Method)
            at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
            at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
            at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
            at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
            at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:482)

I dont know why is it happening, this is my JAVA_HOME,

C700-Notebook-PC:~/Softwares/jdk1.7.0_25/bin$ echo $JAVA_HOME 
/home/ambarish/Softwares/jdk1.7.0_25

Please help in this regard.

Answer 1

Once compiled, you need to move top of the package path (from where the .java have being compiled to an try using the fully qualified name to run the class

java cs.ai.assignment1.EightPuzzle

Not, you should never provide an extension for these as Java will look up the corresponding .class file itself.

nb- This assumes that the EightPuzzle.class file is in the cs/ai/assignment1 directory from where you run the java command

nb- Java assumes that if the file has a package deceleration that the file will reside within the same directory structure as the package deceleration

Answer 2

C700-Notebook-PC:~/aiAssgnmt$ java EightPuzzle.java

This isn't what you want to do. You're sending a java source file to the JVM. You want to send the class file:

java EightPuzzle

Not that you do not specify the .class part

Answer 3

Check the classpath too

Issue -java.lang.NoClassDefFoundError

Root Cause : Incorrect Java path set in Environment Variable Section

Solution : Set correct JAVA_HOME Path

Steps->Environment Variable Setting (My Comp-Right Click ->Properties->Env Variable->Advance Tab ->Variable)

Create new JAVA_HOME Environment Variable.

JAVA_HOME .;C:\\Program Files (x86)\\Java\\jdk1.6.0_14

Set JAVA_HOME variable in PATH Variable section.

PATH %JAVA_HOME%\\bin

Set JAVA_HOME variable in CLASSPATH Variable

CLASSPATH %JAVA_HOME%\\jre\\lib

Restart System

Verify all variable

echo %CLASSPATH%

echo %JAVA_HOME%

echo %PATH%

Compile & Run the program

Additional- Does class H2 in different package ?? then i thing you should check your compiling method