Java version check throws StringIndexOutOfBoundsException on exact major versions

[ato]

Trying out Heritrix on the first JDK 17 release encountered this exception:

$ java -version
openjdk version "17" 2021-09-14
OpenJDK Runtime Environment Temurin-17+35 (build 17+35)
OpenJDK 64-Bit Server VM Temurin-17+35 (build 17+35, mixed mode, sharing)

java.lang.StringIndexOutOfBoundsException: begin 0, end -1, length 2
    at java.base/java.lang.String.checkBoundsBeginEnd(String.java:4601)
    at java.base/java.lang.String.substring(String.java:2704)
    at org.archive.crawler.Heritrix.instanceMain(Heritrix.java:198)
    at org.archive.crawler.selftest.SelfTestBase.startHeritrix(SelfTestBase.java:207)
    at org.archive.crawler.selftest.SelfTestBase.open(SelfTestBase.java:113)
    at org.archive.crawler.selftest.SelfTestBase.testSomething(SelfTestBase.java:151)

I think we should just remove the version check. It's ensuring we're running Java 1.6 or later, but since we target Java 8 for compilation the class can't even be loaded on the old JVMs this check would trigger on, so this code is effectively unreachable.

heritrix3/engine/src/main/java/org/archive/crawler/Heritrix.java

Lines 196 to 204 in 698341a

	// ensure using java 1.6+ before hitting a later cryptic error
	String version = System.getProperty("java.version");
	float floatVersion = Float.valueOf(version.substring(0,version.indexOf('.',2)));
	if(floatVersion<1.6) {
	System.err.println("Heritrix (as of version 3) requires Java 1.6 or higher.");
	System.err.println("You attempted to launch with: "+version);
	System.err.println("Please try again with a later Java.");
	System.exit(1);
	}