How do I resolve ClassNotFoundException?

Question

I am trying to run a Java application, but getting this error:

java.lang.ClassNotFoundException:

After the colon comes the location of the cla

Answer 1

If you have moved your project to new machine or importing it from git, then try this.

1. Right Click on class > Run as > Run Configuration
2. remove main class reference
3. Apply > Close
4. Now again right click on class > run as java application.

It worked for me.

Answer 2

Basic Generic Question - Simplest Generic Answer ;)

Given the information I will make the assumption that you might be trying a basic approach to coding, building/compiling and running a simple console app like "Hello World", using some simple text editor and some Command Shell.

This error occurs in the fallowing scenario:

..\SomePath>javac HelloWorld.java
..\SomePath>java HelloWorld.class

In other words, use:

..\SomePath>java HelloWorld

P.S. The adding the file extension .class produces the same mistake. Also be sure to have the Java's (JDK/JRE) bin folder in the operating system's Environment Variables's PATH.(Lookup for more details other posts on this) P.P.S Was I correct in my assumption/s?

Answer 3

If you know the path of the class or the jar containing the class then add it to your classpath while running it. You can use the classpath as mentioned here:

on Windows

java -classpath .;yourjar.jar YourMainClass

on UNIX/Linux

java -classpath .:yourjar.jar YourMainClass

Answer 4

I just did

1.Invalidate caches and restart

2.Rebuilt my project which solved the problem

Answer 5

If you use maven, check that you have this plugin in your pom.xml:

    <build>
        <plugins>

            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                <version>3.2.0</version>
                <executions>
                    <!-- Attach the shade goal into the package phase -->
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>shade</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>

        </plugins>
    </build>

It will put your dependency (the exception reason) to your jar.

FYI: this will include all dependencies inflated in the final jar

Answer 6

If you have added multiple (Third-Party)**libraries and Extends **Application class

Then it might occur.

For that, you have to set multiDexEnabled true and replace your extended Application class with MultiDexApplication.

It will be solved.