Is Guava's ImmutableList.Builder thread safe?

guava

Solution

While the Guava Immutable classes are threadsafe, their builders are not. For most applications, only one thread will interact with any particular Builder instance.

While the absence of thread-safety usually doesn't need to be documented, such Javadoc might make sense for the Immutable collection builders. People may be surprised that ImmutableList is threadsafe while ImmutableList.Builder isn't.

Problem

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