RFR: 8258422: Cleanup unnecessary null comparison before instanceof check in java.base [v3]

[Chris Hegarty]

On Wed, 16 Dec 2020 09:20:09 GMT, Andrey Turbanov <github.com+741251+turbanoff at openjdk.org> wrote:

>> 8258422: Cleanup unnecessary null comparison before instanceof check in java.base
>
> Andrey Turbanov has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8258422: Cleanup unnecessary null comparison before instanceof check in java.base
>   use instanceof pattern matching in UnixPath too

Let's take advantage of "flow scoping" to eliminate some of these casts. A few examples follow.

src/java.base/share/classes/java/net/InetSocketAddress.java line 414:

> 412:         if (!(obj instanceof InetSocketAddress))
> 413:             return false;
> 414:         return holder.equals(((InetSocketAddress) obj).holder);

If we restructure this a little we can get:

    public final boolean equals(Object obj) {
        if (obj instanceof InetSocketAddress that)
            return holder.equals(that.holder);
        return false;
    }

src/java.base/share/classes/java/net/InetSocketAddress.java line 124:

> 122:             if (!(obj instanceof InetSocketAddressHolder))
> 123:                 return false;
> 124:             InetSocketAddressHolder that = (InetSocketAddressHolder)obj;

If we restructure this a little we can take advantage of flow scoping, e.g.

 public final boolean equals(Object obj) {
            if (!(obj instanceof InetSocketAddressHolder that))
                return false;
            boolean sameIP;
            if (addr != null)
                sameIP = addr.equals(that.addr);
            else if (hostname != null)
                sameIP = (that.addr == null) &&
                    hostname.equalsIgnoreCase(that.hostname);
            else
                sameIP = (that.addr == null) && (that.hostname == null);
            return sameIP && (port == that.port);
        }

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

Changes requested by chegar (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/20