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Filter 51 Chapter 10 ■ Functional Programming reduce performs a reduction on the elements (Figure 10-3).  Reduce limit gives you only the first N elements (Figure 10-4).  Limit 52 Chapter 10 ■ Functional Programming concat combines two different collections of elements (Figure 10-5). 3 Immutability Immutability and FP go together like peanut butter and jelly. Although it’s not necessary, they blend nicely. In purely functional languages, the idea is that each function has no effect outside itself—no side effects.

However, it must be part of a class. Math class we learned about earlier is a static method. To declare a static method, you simply add the word static, as in the following: 1 2 3 public static String makeThemFight(Dragon d, Vampire v) { // a bunch of code goes here. } Because Java is an object-oriented programming language (OOP), in theory, static methods should be used sparingly, because they are not linked to any object. However, in real life, you will see them a lot. ), and it will be interpreted to accept any number of parameters (including zero) and convert them into an array in your method.

Notice how the divide / operator is defined just like any other method. In Groovy, you overload operators by defining methods with special names1 such as plus, minus, multiply, div, etc. org/Operator+Overloading. 4 Actors The actor design pattern is a useful pattern for developing concurrent software. In this pattern, each actor executes in its own thread and manipulates its own data. The data cannot be manipulated by anyone else. Messages are passed between actors to cause them to change data (Figure 9-2).