ConcurrentHashMap JDK 8 when to use computeIfPresent

Question

The new version of Concurrent Hash Map of jdk 8 has two new Methods.

computeIfAbsent

computeIfPresent

putIfAbs

Answer 1

I've used computeIfPresent as a null-safe way to fetch lowercase values from a map of strings.

String s = fields.computeIfPresent("foo", (k,v) -> v.toLowerCase())

Before computeIfPresent was available I'd have to do this:

String s = map.get("foo");
if (s != null) {
    s = s.toLowerCase();
}

Or this:

String s = map.containsKey("foo") ? map.get("foo").toLowerCase() : null;