RFR: 8273261: Replace 'while' cycles with iterator with enhanced-for in java.base

[Andrey Turbanov]

On Wed, 1 Sep 2021 07:37:53 GMT, Andrey Turbanov <github.com+741251+turbanoff at openjdk.org> wrote:

> There are few places in code where manual while loop is used with Iterator to iterate over Collection.
> Instead of manual while cycles it's preferred to use enhanced-for cycle instead: it's less verbose, makes code easier to read and it's less error-prone.
> It doesn't have any performance impact: java compiler generates similar code when compiling enhanced-for cycle.
> 
> Similar cleanups:
> * https://bugs.openjdk.java.net/browse/JDK-8258006
> * https://bugs.openjdk.java.net/browse/JDK-8257912

Tested "tier2" on linux-x86_64-server-fastdebug Ubuntu 21.04

==============================
Test summary
==============================
   TEST                                              TOTAL  PASS  FAIL ERROR   
>> jtreg:test/jdk:tier2                               3772  3771     1     0 <<
   jtreg:test/langtools:tier2                           11    11     0     0   
   jtreg:test/jaxp:tier2                               452   452     0     0   
==============================
TEST FAILURE

Only one test `java/nio/file/FileStore/Basic.java` failed, but it fails without my changes too.

----------System.out:(46/2591)----------

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PR: https://git.openjdk.java.net/jdk/pull/5328