RFR: 8266675: Optimize IntHashTable for encapsulation and ease of use

[Guoxiong Li]

Hi all,

Currently, the class `com.sun.tools.javac.util.IntHashTable` exposes methods `hash(Object key)` and `lookup(Object key)` to users. It is not good because they are internal methods to achieve the features.

On the other hand, the index of the mapping (key or value) is the internal data struct. The users should not know or use it actually. So the parameters of the following methods should be revised.

1. lookup(Object key, int hash) -> lookup(Object key)
2. getFromIndex(int index) -> get(Object key)
3. putAtIndex(Object key, int value, int index) -> put(Object key, int value)

And the corresponding places where they are used need to be adjusted too.

The patch optimizes them, adds some comments and cleans the code.
Thank you for taking the time to review.

Best Regards,
-- Guoxiong

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Commit messages:
 - Update copyright
 - 8266675: Optimize IntHashTable for encapsulation and ease of use

Changes: https://git.openjdk.java.net/jdk/pull/3912/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3912&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8266675
  Stats: 46 lines in 2 files changed: 10 ins; 19 del; 17 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3912.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3912/head:pull/3912

PR: https://git.openjdk.java.net/jdk/pull/3912