I'm reading OCP study guide (OCP_ Oracle Certified Professional
Java SE 8 Programmer II Study Guide), in chapter 7, in a part talking about
Using the One-Argument collect() Method, it is said that in order for reduction to be performed effeciently these requirments need to be fulfilled :
■■ The stream is parallel.
■■ The parameter of the collect operation has the Collector.Characteristics.CONCURRENT characteristic.
■■ Either the stream is unordered, or the collector has the characteristic Collector.Characteristics.UNORDERED.
So I wonder how to verify if a data structure fulfill the last 2 rules, for example I tried for the
ConcurrentHashMap that is said to fulfill them but I didn't find any thing