Incompatible magic value 0 ASM

I have a .class file that is being generated using ASM core API in the following way:

public void createEmptyClassWithinPackage(String packageName, String className){
    /* Creating ClassWriter object that creates class in bytecode representation
    *  Flag 0 - no need in computation of stack size and generation of frames */
    ClassWriter classWriter = new ClassWriter(0);
    ClassVisitor classVisitor = new ClassVisitor(ASM4, classWriter) { };

    // Visiting class declaration: version, access, name, generic, super, interface
    classVisitor.visit(V9, ACC_PUBLIC, packageName + className, null,
            Type.getInternalName(Object.class), null);

    // Indicate that generation of class is done and get byte array
    classVisitor.visitEnd();
    classWriter.visitEnd();
    byte[] bytesOfClassToWrite = classWriter.toByteArray();

    checkClassPackage(packageName);
    writeClassToPackage(packageName, className, bytesOfClassToWrite);
}

Methods at the end just check the directory and write the .class file into it. Later when I want to add something to the class I am using:

public void writeEmptyConstructor(String packageName, String className){
    /* Read generated class form package and generate empty constructor */
    byte[] bytesOfClassToRead = readClassFromPackage(packageName, className);

    ClassReader classReader = new ClassReader(bytesOfClassToRead);
    ClassWriter classWriter = new ClassWriter(classReader, ClassWriter.COMPUTE_FRAMES);
    ClassVisitor classVisitor = new ClassVisitor(ASM4, classWriter) { };
    classReader.accept(classVisitor, 0);

    generateDefaultConstructor(classVisitor);

    // Indicate that generation of constructor is done and get byte array
    classVisitor.visitEnd();
    classWriter.visitEnd();
    byte[] bytesOfClassToWrite = classWriter.toByteArray();

    writeClassToPackage(packageName, className, bytesOfClassToWrite);
}

The problem appears when I try to read Class using ClassLoader:

File file = new File("result/classes/TestClass.class");
try(FileInputStream fileInputStream = new FileInputStream(file)) {
    byte[] classByteArray = new byte[(int) file.length()];
    GeneratedClassLoader generatedClassLoader = new GeneratedClassLoader();
    Class c = generatedClassLoader.defineClass("result.classes.TestClass", classByteArray);
} catch (FileNotFoundException e) {
    e.printStackTrace();
} catch (IOException e) {
    e.printStackTrace();
}

The code above gives an error:

Exception in thread "main" java.lang.ClassFormatError: Incompatible magic value 0 in class file result/classes/TestClass
    at java.base/java.lang.ClassLoader.defineClass1(Native Method)
    at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1017)
    at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:878)
    at callers.GeneratedClassLoader.defineClass(GeneratedClassLoader.java:5)
    at Main.main(Main.java:28)

But when I try to use ClassLoader without writing byte array on a disc it works perfectly fine:

    public void createEmptyClassWithinPackage(String packageName, String className){
        /* Creating ClassWriter object that creates class in bytecode representation
        *  Flag 0 - no need in computation of stack size and generation of frames */
        ClassWriter classWriter = new ClassWriter(0);
        ClassVisitor classVisitor = new ClassVisitor(ASM4, classWriter) { };

        // Visiting class declaration: version, access, name, generic, super, interface
        classVisitor.visit(V9, ACC_PUBLIC, packageName + className, null,
                Type.getInternalName(Object.class), null);

        // Indicate that generation of class is done and get byte array
        classVisitor.visitEnd();
        classWriter.visitEnd();
        byte[] bytesOfClassToWrite = classWriter.toByteArray();

        GeneratedClassLoader generatedClassLoader = new GeneratedClassLoader();
        Class c = generatedClassLoader.defineClass((packageName + className).replace("/", ".")
                , bytesOfClassToWrite);

//        checkClassPackage(packageName);
//        writeClassToPackage(packageName, className, bytesOfClassToWrite);
    }

My question is: What happens to magic value when I read class from a disc? May it be that I should not use ClassLoader and use something else to read .class files as a byte array from the disc?

The solution was simple, I forgot to write:

fileInputStream.read(classByteArray);

I will not delete this post, hope someone will find it useful.