RFR: 6323374: (coll) Optimize Collections.unmodifiable* and synchronized*

[Roger Riggs]

On Tue, 16 Feb 2021 21:57:43 GMT, Ian Graves <igraves at openjdk.org> wrote:

> Modify the `unmodifiable*` methods in `java.util.Collections` to be idempotent. That is, when given an immutable collection from `java.util.ImmutableCollections` or `java.util.Collections`, these methods will return the reference instead of creating a new immutable collection that wraps the existing one.

Please add a space after `if` ->  `if `.

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PR: https://git.openjdk.java.net/jdk/pull/2596