Method reference

To improve code readability of Lambda expressions for functions having a name method reference is used. Method references have been identified in four different categories:

• Static method reference: For a static method isOdd, the method can be directly referenced as MethodReferenceExample::isOdd:

public static boolean isOdd(Integer n) { return n % 2 != 0; };
public static void main(String[] args) {
IntStream.range(1, 8).filter(MethodReferenceExample::isOdd).forEach(x->System.out.println(x));
}

• Instance method reference: For referencing an instance method, the instance of the method can be called separated by a double colon (::). Here System.out is an instance of PrintStream whose method println is being called:

//Instance Method Reference
IntStream.range(1, 8).filter(x-> x%2==0).forEach(System.out::println);

• Constructor reference: A constructor method reference can be called by adding the suffix new after :::

//Constructor Reference
TreeSet<String> hset= streamSupplier.get().collect(Collectors.toCollection(TreeSet::new));

1. Instance method reference of an arbitrary object of a particular type: The following example is an instance method reference of an arbitrary object of a particular type:

System.out.println(" The sum of lengths are ::" + streamSupplier.get().map(x->x.length()).reduce(Integer::sum));