Replace dead javadoc links with www.javadoc.io links.

JSR-305 doesn't have 2.0.1 JavaDoc, it is pointing at the 3.0.1 release as the first release thereafter that does.

Also fixed doc generation when building under Java 9 and later.

Author: Capstan

build.gradle

@@ -68,12 +68,20 @@ dependencies {
     testCompile(group: "org.mockito", name: "mockito-core", version: "1.9.5");
 }
 
-javadoc.options.links("http://docs.oracle.com/javase/6/docs/api/");
-javadoc.options.links("http://jsr-305.googlecode.com/svn/trunk/javadoc/");
-javadoc.options.links("http://fasterxml.github.com/jackson-databind/javadoc/2.2.0/");
-javadoc.options.links("http://docs.guava-libraries.googlecode.com/git-history/v16.0.1/javadoc/");
-javadoc.options.links("http://fge.github.io/msg-simple/");
-
+javadoc {
+    options {
+        def currentJavaVersion = org.gradle.api.JavaVersion.current()
+        // FIXME: https://github.com/gradle/gradle/issues/11182
+        if (currentJavaVersion.compareTo(org.gradle.api.JavaVersion.VERSION_1_9) >= 0) {
+            addStringOption("-release", "6");
+        }
+        links("https://docs.oracle.com/javase/6/docs/api/");
+        links("https://www.javadoc.io/doc/com.google.code.findbugs/jsr305/3.0.1/");
+        links("https://fasterxml.github.com/jackson-databind/javadoc/2.2.0/");
+        links("https://www.javadoc.io/doc/com.google.guava/guava/16.0.1/");
+        links("https://fge.github.io/msg-simple/");
+    }
+}
 
 /*
  * Necessary! Otherwise TestNG will not be used...