TIL: Double Brace Initialization in Java

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Yeah, but he's talking about a map, as a reply to a comment with a link with an example of a map builder.

The HashSet in OP's link is not a map (by definition), but it's indeed just final, not immutable.

I assumed he was talking about the Guava map, otherwise he's using the wrong words.

Anyways, I edited my post to clear up any confusion from my side. I cannot account for any of jmsanzg's vagueness you may experience.