RFR: 8260428: Drop support for pre JDK 1.4 DatagramSocketImpl implementations

[Patrick Concannon]

Hi,

Could someone please review my changes (and CSR) to drop support for pre JDK 1.4 `DatagramSocketImpl` implementations?

These changes propose to drop support for `DatagramSocketImpls` that were compiled with JDK 1.3 or older, which do not have support for connected sockets, for peeking at received datagrams, and for joining and leaving a group at a specific interface. This support is legacy, and should be relatively safe to remove as such implementations do not compile with JDK 1.4 or newer.

Finally, with this set of proposed changes, if you have an `oldImpl`, and don’t use connect, then the methods `joinGroup` and `leaveGroup` will throw `NoSuchMethodError`.  However, the current behaviour in `DatagramSocketImpl` is to throw an `UnsupportedOperationsException` for a method not implemented. Should this set of changes update the `joinGroup` and `leaveGroup` methods in order to preserve this behaviour?

CSR: https://bugs.openjdk.java.net/browse/JDK-8274633

Kind regards,

Patrick

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Commit messages:
 - 8260428: Drop support for pre JDK 1.4 DatagramSocketImpl implementations

Changes: https://git.openjdk.java.net/jdk/pull/5887/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5887&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8260428
  Stats: 346 lines in 3 files changed: 258 ins; 74 del; 14 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5887.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5887/head:pull/5887

PR: https://git.openjdk.java.net/jdk/pull/5887