Is there a Java equivalent of Python's defaultdict?

Question

In Python, the defaultdict class provides a convenient way to create a mapping from key -> [list of values], in the following example,

from collections import defaultdict
d = defaultdict(list)
d[1].append(2)
d[1].append(3)
# d is now {1: [2, 3]}

Is there an equivalent to this in Java?

user_3151415 · Answer

In Java 8+ you can use:

map.computeIfAbsent(1, k -> new ArrayList()).add(2);