Error when executing Java code with nested class

Question

newbie here. Tried executing Java class that has a nested class and I keep getting this Error: Could not find or load main class . Caused by: java.lang.ClassNotFoundException When I compiled the source code, I got two new .class files; ShadowTest$FirstLevel.class and ShadowTest.class. The error shows up when I try to execute either one. Please help.

Here's the code

public class ShadowTest {

    public int x = 0;

    class FirstLevel {

        public int x = 1;

        void methodInFirstLevel(int x) {
            System.out.println("x = " + x);
            System.out.println("this.x = " + this.x);
            System.out.println("ShadowTest.this.x = " + ShadowTest.this.x);
        }
    }

    public static void main(String... args) {
        ShadowTest st = new ShadowTest();
        ShadowTest.FirstLevel fl = st.new FirstLevel();
        fl.methodInFirstLevel(23);
    }
}

Which command do you use to compile and then run the file(s)? — knittl, Jul 17 '21 at 06:20

score 1 · Answer 1 · answered Jul 17 '21 at 08:18

I tried to replicate the issue you are facing by following the below steps.

I have created a java file "ShadowTest.java" with your code.

public class ShadowTest {

    public int x = 0;

    class FirstLevel {

        public int x = 1;

        void methodInFirstLevel(int x) {
            System.out.println("x = " + x);
            System.out.println("this.x = " + this.x);
            System.out.println("ShadowTest.this.x = " + ShadowTest.this.x);
        }
    }

    public static void main(String... args) {
        ShadowTest st = new ShadowTest();
        ShadowTest.FirstLevel fl = st.new FirstLevel();
        fl.methodInFirstLevel(23);
    }
}

Compiled the ShadowTest.java using javac ShadowTest.java, two class files were created

D:\test>javac ShadowTest.java

D:\test>dir
Volume in drive D is MonWork
Volume Serial Number is 3A72-52A4

Directory of D:\test

17-07-2021 13:01 .
17-07-2021 13:01 ..
17-07-2021 13:01 901 ShadowTest$FirstLevel.class
17-07-2021 13:01 529 ShadowTest.class
17-07-2021 13:01 539 ShadowTest.java
3 File(s) 1,969 bytes
2 Dir(s) 55,102,857,216 bytes free

output of javac command and newly created class files in the same directory

On executing ShadowTest class, with java ShadowTest command. I am getting the expected output.
OUTPUT:
D:\test>java ShadowTest
x = 23
this.x = 1
ShadowTest.this.x = 0
output of java command and its output
To reproduce your issue I tried to delete ShadowTest$FirstLevel.class file and execute java ShadowTest. But did not get the exact error you are getting.

Error: Could not find or load main class . Caused by: java.lang.ClassNotFoundException

*D:\test>del ShadowTest$FirstLevel.class

D:\test>java ShadowTest
Exception in thread "main" java.lang.NoClassDefFoundError: ShadowTest$FirstLevel
        at ShadowTest.main(ShadowTest.java:18)
Caused by: java.lang.ClassNotFoundException: ShadowTest$FirstLevel
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        ... 1 more*

executing main class after deleting the class file for the inner class.

Please share the complete error message and commands you are using for compiling and executing the class.

It was just a scenario to reproduce the issue. According to the post the root cause was Caused by: java.lang.ClassNotFoundException. So deleting the class file after compilation was a way to get the exception. — Shashi Shankar, Jul 17 '21 at 08:26
I just ran it the way you and it worked. I realised my mistake, the previous tutorial I did used assert statements, so instead of using -cp at the command line, I kept using -ea. My bad for the inconvenience, but learnt a lot thought, thank you. — Ten Kei, Jul 17 '21 at 08:46

score 0 · Accepted Answer · answered Jul 17 '21 at 06:32

You can always compile the class with javac filename command. Then execute the code with command java main_class_name

javac ShadowTest.java
java ShadowTest

/** output **/

x = 23
this.x = 1
ShadowTest.this.x = 0

Inner classes, if any present in your class, will be compiled and the class file will be ClassName$InnerClassName.

score 0 · Answer 3 · answered Jul 17 '21 at 07:23

0

use this online compiler ,it's executing your code error free

your code:

output :

answered Jul 17 '21 at 07:23

saqib kafeel

296
3
8

Error when executing Java code with nested class

3 Answers3