[FIXED] java11 allows the compilation and execution in a single line

Issue

in a file named filename.java

class filename{
public static void main(String[] a){
System.out.println("From filename main method");
}
}

public class ClassName{
public static void main(String[] a){
System.out.println("From First main method");
}
}

Observe below commands:

Command 1:

C:\javaDJ>java filename.java
From filename main method

Command 2:

C:\javaDJ>javac filename.java
filename.java:7: error: class ClassName is public, should be declared in a file named ClassName.java
public class ClassName{
      ^
1 error

Observation:

command 1 compiles (i assume internally ) and executes successfully.
command 2 throws compilation error.

Problem Statement :

How is java cmd able to compile the file called filename.java, when the file(filename.java) contains a public class (ClassName)which is not named 'filename.java' (the name of the file-name.) ?

Solution

To highlight a specific section from the JEP#Launch Single-File Source-Code Programs with regards to the behavior

In source-file mode, execution proceeds as follows:

• The class to be executed is the first top-level class found in the source file. It must contain a declaration of the standard public static void main(String[]) method.

Answered By - Naman
Answer Checked By - Pedro (JavaFixing Volunteer)