找不到类ImmutableSettings

In ES 2.0, the

ImmutableSettings

class
was indeed removed. This issue mentions it and thebreaking
changes documentation for 2.0 also mention it.

Instead you can now use

Settings.builder()

instead
of

ImmutableSettings.builder()

.
The current implementation of the

Settings

class
can be seen here

All the questions that still use

ImmutableSettings

are
questions about pre-2.0 versions of Elasticsearch.