Error: Could not find or load main class

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What does “Could not find or load main class” mean? 39 answers

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You must ensure that you add the location of your .class file to your classpath. So, if its in the current folder then add . to your classpath. Note that the windows classpath separator is a semi-colon ie ;

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If the class is in a package

package thepackagename;

public class TheClassName {
  public static final void main(String[] cmd_lineParams)  {
     System.out.println("Hello World!");
  } 
}

Then calling:

java -classpath . TheClassName

results in Error: Could not find or load main class TheClassName . This is because it must be called with its fully-qualified name:

java -classpath . thepackagename.TheClassName

And this thepackagename directory must exist in the classpath. In this example, . , meaning the current directory, is the entirety of classpath. Therefore this particular example must be called from the directory in which thepackagename exists.

To be clear, the name of this class is not TheClassName , It's thepackagename.TheClassName . Attempting to execute TheClassName does not work, because no class having that name exists. Not on the current classpath anyway.

Finally, note that the compiled (.class) version is executed, not the source code (.java) version. Hence “CLASSPATH.”

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You can try these two when you are getting the error: 'could not find or load main class'

If your class file is saved in following directory with HelloWorld program name d:sample

java -cp d:sample HelloWorld

java -cp . HelloWorld

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