DDevelopment & Design

TouK contest – some important rules

By entering TouK contest at 33rd Degree Conference you are accepting these simple conditions:

  1. The contest is open to all 33rd Degree Conference participians, except TouK people and their family members, of course (sorry, guys).
  2. To take part, you must collect two TouK feathers (in two different colours) and hack an application. The apllication is avaliable at http://reg.touk.pl. Then you must write down the solution (with your name and surname) on a sheet of paper received at our stand. and leave it to us to enter a prize draw. You must have TouK feathers in both colors with you.
  3. Only one entry is allowed per person.
  4. The prizes are 6 Raspberry Pi computers (2 per each conference day).
  5. All entries (except the winners’) will be rolled over into subsequent draws.
  6. All prize draws take place at our stand in following dates: ·Day 1, 13 of March – 16:30 ·Day 2, 14 of March – 15:50 ·Day 3, 15 of March – 12:50
  7. Only correct and complete solutions will be awarded.
  8. The winner have to be present during the prize draw. If not, we reserve the right to award the prize to an alternative winner, drawn in accordance with these terms and conditions.
  9. If you have any questions about how to enter or in connection with the contest, please ask at TouK’s stand.

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Thanks for visiting TouK stand at the 33rd Degree Conference

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DDevelopment & Design

Private fields and methods are not private in groovy

I used to code in Java before I met groovy. Like most of you, groovy attracted me with many enhancements. This was to my surprise to discover that method visibility in groovy is handled different than Java!

Consider this example:

class Person {
private String name
public  String surname

private Person() {}

private String signature() { "${name?.substring(0, 1)}. $surname" }

public String toString() { "I am $name $surname" }
}

How is this class interpreted with Java?

  1. Person has private constructor that cannot be accessed
  2. Field "name" is private and cannot be accessed
  3. Method signature() is private and cannot be accessed

Let's see how groovy interpretes Person:

public static void main(String[] args) {
def person = new Person()   // constructor is private - compilation error in Java
println(person.toString())

    person.@name = 'Mike'       // access name field directly - compilation error in Java
println(person.toString())

    person.name = 'John'        // there is a setter generated by groovy
println(person.toString())

    person.@surname = 'Foo'     // access surname field directly
println(person.toString())

    person.surname = 'Bar'      // access auto-generated setter
println(person.toString())

println(person.signature()) // call private method - compilation error in Java
}

I was really astonished by its output:

I am null null
I am Mike null
I am John null
I am John Foo
I am John Bar
J. Bar

As you can see, groovy does not follow visibility directives at all! It treats them as non-existing. Code compiles and executes fine. It's contrary to Java. In Java this code has several errors, pointed out in comments.

I've searched a bit on this topic and it seems that this behaviour is known since version 1.1 and there is a bug report on that: http://jira.codehaus.org/browse/GROOVY-1875. It is not resolved even with groovy 2 release. As Tim Yates mentioned in this Stackoverflow question: "It's not clear if it is a bug or by design". Groovy treats visibility keywords as a hint for a programmer.

I need to keep that lesson in mind next time I want to make some field or method private!