RFR: 8287497: Use String.contains() instead of String.indexOf() in java.naming

[Raffaello Giulietti]

On Sun, 29 May 2022 14:00:20 GMT, Andrey Turbanov <aturbanov at openjdk.org> wrote:

> `String.contains` was introduced in Java 5.
> Some code in java.naming still uses old approach with `String.indexOf` to check if String contains specified substring.
> I propose to migrate such usages. Makes code shorter and easier to read.

_(not a reviewer)_
Provided `indexOf() != -1` and `indexOf() >= 0` are equivalent (which should indeed be the case, according to the Javadoc), the changes look good

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PR: https://git.openjdk.java.net/jdk/pull/8938