RFR: 8252999: replace all String.equals("") usages with String.isEmpty()

[Sergey Bylokhov]

On Sun, 6 Sep 2020 13:57:19 GMT, Dmitriy Dumanskiy <github.com+1536494+doom369 at openjdk.org> wrote:

> **isEmpty** is faster + has less byte code + easier to read. Benchmarks could be found
>   [here](https://medium.com/javarevisited/micro-optimizations-in-java-string-equals-22be19fd8416).

src/demo/share/java2d/J2DBench/src/j2dbench/tests/iio/InputImageTests.java line 187:

> 185:             String format = spi.getFormatNames()[0].toLowerCase();
> 186:             String suffix = spi.getFileSuffixes()[0].toLowerCase();
> 187:             if (suffix == null || suffix.equals("")) {

This file intentionally maintains compatibility to jdk1.4, so equals("") should be used.

src/demo/share/java2d/J2DBench/src/j2dbench/tests/iio/OutputImageTests.java line 146:

> 144:             String format = spi.getFormatNames()[0].toLowerCase();
> 145:             String suffix = spi.getFileSuffixes()[0].toLowerCase();
> 146:             if (suffix == null || suffix.equals("")) {

This file intentionally maintains compatibility to jdk1.4, so equals("") should be used.

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PR: https://git.openjdk.java.net/jdk/pull/29