repr(x)

x.inspect(), x.dump()

x.y if x else None

x?.y

"%(foo)s" % locals()

"${foo}"

not x

!x
x.empty

len(x)

x.size()

for item, idx in enumerate(x): ...

x.eachWithIndex { item, idx -> ... }

{}

[:] // an empty map

Depends:
d if used like:  for k in d:
list(d) if list needed
d.[iter]keys() explicitly

d.keySet()

d.[iter]values()

d.values()

[k+1 for k in d]

d.collect { k, v -> k+1 }

d = dict(zip(k, v))

k = 1..3
v = 'a'..'c'
d = [:]; k.eachWithIndex { it, i -> d[it] = v[i] }
println d // [1:"a", 2:"b", 3:"c"]

range(3)

0..<3

range(1, 3+1)

1..3

range(0, 10, 2)

0.step(10, 2) {...}

"abcdef"[3:]

"abcdef"[3..-1]

m = 'strip'; getattr(' ! ', m)()

m = 'trim'; ' ! '."$m"()

args = ('a', 2); 'abcabc'.find(*args)

args = ['a', 2]; 'abcabc'.indexOf(*args)