Differences between StringBuffer.append und String +

Hm,... so other versions of the script:

class Test {
public String toString() { super.toString() + properties.toString() }
}
println new Test()

and

class Test {
public String toString() { super.toString() << properties }
}
println new Test()

produce the second result again:
Test@13c1b02{metaClass=groovy.lang.MetaClassImpl@91cee[class Test], class=class Test}

So, is something wrong with the + operator for Strings in scripts?

PS: I used Groovy 1.5.0

Just summarising, this code:

class Test1 {
  public String toString() { super.toString() + properties.toString() }
}
println new Test1()

class Test2 {
  public String toString() { super.toString() << properties }
}
println new Test2()

class Test3 {
  public String toString() { super.toString() + properties }
}
println new Test3()

class Test4 {
  public String toString() { new StringBuffer(super.toString()).append(properties) }
}
println new Test4()

class Test5 {
    public String toString() { "${super.toString()}${properties}" }
}
println new Test5()

produces these results:

Test1@1acd47{metaClass=groovy.lang.MetaClassImpl@ff2413[class Test1], class=class Test1}
Test2@104c575{metaClass=groovy.lang.MetaClassImpl@3fa5ac[class Test2], class=class Test2}
Test3@1e58cb8[metaClass:groovy.lang.MetaClassImpl@179935d[class Test3], class:class Test3]
Test4@67064{metaClass=groovy.lang.MetaClassImpl@c5495e[class Test4], class=class Test4}
Test5@914f6a[metaClass:groovy.lang.MetaClassImpl@16d2633[class Test5], class:class Test5]

This is using 1.5.2-SNAPSHOT and is slightly different to what 1.5.0 gives you. The issue isn't
anything to do with the + operator per se or whether the script is compiled. It is simply whether
the artifact is being "pretty printed" by Java or Groovy. Groovy tries to produce a prettier looking
format for maps but sometimes Java is calling Java and bypassing Groovy's mechanics for
swapping in the prettier version.

See also the related GROOVY-2331.

as Paul said the issue is not related to the "+" operator