i have a project, and i am build this project with jdk 6,7,8 and my target is 1.6
when i build jdk 8 i get this error:
Undefined reference: java.util.concurrent.ConcurrentHashMap.KeySetView java.util.concurrent.ConcurrentHashMap.keySet()
since i have this code in that line:
final Iterator<CLASS_NAME> itr = hashMap.keySet().iterator();
how can avoid error, i made some search in internet, and since java 8 changed its return type keyset, i got error. is this any solution. i am using maven, and animal-sniffer-plugin gives this error, with signature error.
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Answer
Another Answer suggests a modification to your code (using keys() instead of keySet()) so that you can compile your source code on Java 8 and run on Java 7. I think that is a retrograde step.
Instead:
If your aim is to create a production build of your software that will run on Java 6, 7 and 8, then your best bet is to do your production builds on JDK 6.
If your aim is to do your development builds on Java 8 (but stay backwards compatible at the source code level for now), then change the maven plugin configs for animal-sniffer to ignore these classes; see http://mojo.codehaus.org/animal-sniffer-maven-plugin/examples/checking-signatures.html for an explanation.
However, there is a risk that animal-sniffer will ignore too much; e.g. it won’t tell you if you use new Java 8 methods in
ConcurrentHashMap. You will need to allow for that possibility ….If your aim is to move to Java 8 (so that you can start using new Java 8 features in your code), then just do it. Your code won’t be backward compatible, but you can’t support old versions of Java for ever …
(These suggestions are not mutually exclusive, if you consider the big picture.)