Why java.exe on windows tries to find a class name in lowercase though it is in camel-case?

Java fails to load a simple HelloWorld example on my PC(Windows 10, Java 8). I cannot find any system environmental changes that may cause this problem.

HelloWorld.java

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello, World!!!");
    }
}

Command Prompt

D:\Temp>javac HelloWorld.java

D:\Temp>java -classpath . HelloWorld
Error: Cound not find or load main class helloworld.

D:\Temp>echo %JAVA_HOME%
C:\Program Files\Java\jdk1.8.0_261

D:\Temp>where java
C:\Program Files\Java\jdk1.8.0_261\bin\java.exe
C:\Program Files (x86)\Common Files\Oracle\Java\javapath\java.exe
C:\Windows\System32\java.exe

D:\Temp>dir HelloWorld.*
2022-07-14  am 09:38               429 HelloWorld.class
2022-07-14  am 09:37               131 HelloWorld.java

The same class file works without problem in a test server (CentOS 7, Java 8).

$ java -classpath . HelloWorld
Hello, World!!!

One strange thing is that the class name in lowercase works well like the following:

helloworld2.java

public class helloworld2 {
    public static void main(String[] args) {
        System.out.println("Hello, World 2!!!");
    }
}

Command Prompt

D:\Temp>javac helloworld2.java

D:\Temp>java helloworld2
Hello, World 2!!!

Could anybody help me to find a resolution?

Edit After Post

I remember that the system was automatically rebooted (maybe for update) before the problem started.

The problem continued after system reboot but disappered after system shutdown and then boot.