[GROOVY-9595] Groovy final keyword behaves more like Immutable, doesn't follow java's final keyword behaviour

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Not A Bug
• Affects Version/s: 2.5.6, 3.0.4
• Component/s: Compiler
• Assignee: Unassigned
• Reporter: Abhiyank
• Created: 16/Jun/20 12:32
• Updated: 16/Jun/20 13:59
• Resolved: 16/Jun/20 13:25

Description

i think we need to re-open this ticket, the way final keyword behaves is not right.

A final object is not Immutable, you can call accessor methods on it, which is broken now:

Consider following code:

class TestGroovy {

    public static void main(String[] args) {
        final Set<String> testSet = []
        for (int i = 0; i < 4; i++) {
            testSet += "asd" + i
        }

        println testSet
    }

}

Which results in following output:

PS E:\Projects> groovy -v
Groovy Version: 3.0.4 JVM: 1.8.0_221 Vendor: Oracle Corporation OS: Windows Server 2019
PS E:\Projects> groovy .\TestGroovy.groovy
org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
E:\Projects\TestGroovy.groovy: 6: The variable [testSet] is declared final but is reassigned
. At [6:13]  @ line 6, column 13.
               testSet += "asd" + i
               ^

1 error

So if the Set object is not Immutable why can't it be modified? Similar results are observed when you try to set a final object's field.
We should be following Java's definition of final. I think this article covers the final behaviour in detail: https://www.baeldung.com/java-final

Issue Links

• is caused by: GROOVY-1628 Inconsistent checking of final