Collectors

Class Collectors

• Collectors is a final class that extends the Object class.
• Collectors is one of the utility class in JDK which contains a lot of utility functions.
• It is mostly used with Stream API as a final step.
• Functions associated with Collectors usually get used inside collect() methods.
• Collectors class is part of Stream package and can be imported as:

import static java.util.stream.Collectors.*;

//java.lang.Object
//    ↳ java.util.stream
//        ↳ class Collectors

Running Examples

• Java-8 Streams Collectors

🗃️ groupingBy

3 items

📄️ joining

joining()

📄️ partitioningBy

Collectors **partitioningBy()** method is a predefined method of java.util.stream. Collectors class which is used to partition a stream of objects(or a set of elements) based on a given predicate. There are two overloaded variants of the method that are present. One takes only a predicate as a parameter whereas the other takes both predicate and a collector instance as parameters.

📄️ reducing

The overloaded static methods, Collectors.**reducing()** return a Collector which perform a reduction on the input stream elements according to the provided binary operator.

📄️ summarizing

**summarizingDouble()**

📄️ summing

**summingDouble()**