RFR: 8286378: Address possibly lossy conversions in java.base [v2]

[Roger Riggs]

> PR#8599 8244681: proposes to add compiler warnings for possible lossy conversions
> From the CSR:
> 
> "If the type of the right-hand operand of a compound assignment is not assignment compatible with the type of the variable, a cast is implied and possible lossy conversion may silently occur. While similar situations are resolved as compilation errors for primitive assignments, there are no similar rules defined for compound assignments."
> 
> This PR anticipates the warnings and adds explicit casts to replace the implicit casts.
> In most cases, the cast matches the type of the right-hand side to type of the compound assignment.
> Since these casts are truncating the value, there might be a different refactoring that avoids the cast
> but a direct replacement was chosen here.
> 
> (Advise and suggestions will inform similar updates to other OpenJDK modules).

Roger Riggs has updated the pull request incrementally with one additional commit since the last revision:

  remove stray file

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8642/files
  - new: https://git.openjdk.java.net/jdk/pull/8642/files/e72ce85c..7ff806a5

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8642&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8642&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 1 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8642.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8642/head:pull/8642

PR: https://git.openjdk.java.net/jdk/pull/8642