Errata OCP Java SE 11 Programmer I Study Guide - Single-file Source-code Command

[ilkay Polat]

Hi,

Errata OCP Java SE 11 Programmer I Study Guide, in page 13, in table 1.1, It is written that Single-file source-code command is for programs with one class. But it should be written as `For programs with one file`.

It will be better in this way. Because there may be more than one class in a java file.

[Jeanne Boyarsky]

I agree. I've added this to errata. I actually had the same rror on page 12 in the text. That was added to the errata in January.

(This error from me not knowing how this feature worked for a multi class file until after the book printed. I like the feature but use it for simple programs in real life)

[Bassam Gemayel]

Hey Jeanne, Ilkay,

The java MyClasses.java option ONLY works for a SINGLE class in the file MyClasses.java.

It is the FIRST class that is declared.

If you have 2 or more classes, they are ignored.

You cannot extend another class in the file MyClasses.java.

If the first declared class extends another class in the same file MyClasses.java, the command will fail.

Hope this helps and thanks,

Bassam

[Jeanne Boyarsky]

Bassam,
Welcome to CodeRanch! While I agree the main method must be in the first class, it can reference other classes in the file. The following works:

class Jeanne {
  public static void main(String[] args) {
    Parent p = new Child();
    System.out.println("Hello ");
  }
}
class Child extends Parent {
}

class Parent {
}

[Bassam Gemayel]

Brilliant! Did not even think about trying this! :-)

Thus, you CAN have multiple classes in the file and they are compiled.

Thank you, Jeanne!

PS.: You and Scott created a gem, I learned faster and more accurately reading your book than I ever did reading any other Java material, kudos!