class is one of the keyword, but you are tyring to use as a variable name
SecondClass class = new SecondClass();
class.HelloWorld();
Please change the variable name to different name than class and retry.
You cannot use keywords like int, for, class, etc as variable name (or identifiers) as they are part of the Java programming language syntax.
I made following changes and the ran successfully
public class FirstClass {
public static void main(String[] args) {
SecondClass class1 = new SecondClass();
class1.HelloWorld();
}
}
Directory of D:\workspace_europa\DatastructureAndAlgorithms\src
09/13/2020 10:06 AM <DIR> .
09/13/2020 10:06 AM <DIR> ..
09/13/2020 10:11 AM 330 FirstClass.class
09/13/2020 10:06 AM 168 FirstClass.java
09/13/2020 10:11 AM 408 SecondClass.class
09/13/2020 09:57 AM 131 SecondClass.java
D:\workspace_europa\DatastructureAndAlgorithms\src>d:\InstalledProgramms\Java\jdk1.5.0_22\bin\javac.exe -cp . FirstClass.java
D:\workspace_europa\DatastructureAndAlgorithms\src>d:\InstalledProgramms\Java\jdk1.5.0_22\bin\javac.exe -cp . FirstClass.java
D:\workspace_europa\DatastructureAndAlgorithms\src>d:\InstalledProgramms\Java\jdk1.5.0_22\bin\java.exe -cp . FirstClass
Hello World
If you are still facing issue then using -verbose flag during compilation and runtime can give you the lead
D:\workspace_europa\DatastructureAndAlgorithms\src>d:\InstalledProgramms\Java\jdk1.5.0_22\bin\javac.exe -verbose -cp . FirstClass.java
D:\workspace_europa\DatastructureAndAlgorithms\src>d:\InstalledProgramms\Java\jdk1.5.0_22\bin\java.exe -verbose -cp . FirstClass