Reuse Java's closures/anonymous classes for performance?

Question

When I use anonymous classes for small operations like filtering a collection, there is memory allocation for a new anonymous class instance or closure in Java 8.

String firstNonEmpty = Lists.find(list, new Predicate<String>(){
     public String apply(String s){ return !s.isEmpty();}
});

Should I reuse such a predicate or a closure in Java 8? Always/in a cycle/in a GC-free method?

Answer 1

Creating many small objects is close to free (allocation and GC), with the caveat that GC will run more often, so there is a slight performance cost associated with it. Creating anonymous inner classes also has specific issues - this question has several answers that address that aspect.

However creating a lambda, as in:

String firstNonEmpty = Lists.find(list, (s) -> !s.isEmpty());

does not necessarily create a new object. In particular, for stateless lambdas like that one, the JVM should only create one lambda "object" and reuse it.