Understand the functional programming paradigm in the Java class library

The understanding and application of the functional programming paradigm in the Java library Functional programming paradigm is a way to write code, emphasizing the use and combination of functions, not a traditional object -based programming method.After introducing Lambda expressions and function interfaces, the Java class library also began to support functional programming paradigms.This article will introduce the characteristics of functional programming in the Java class library and use examples. 1. Lambda expression Lambda expression is one of the core concepts of functional programming.It can represent anonymous functions with simple grammar and can be passed directly in the expression.Lambda expression syntax is as follows: (parameter1, parameter2, ..., parameterN) -> { // Lambda expression execution body // You can use the parameters to perform some operations and return the result } Lambda expressions can be used in functional interfaces. Functional interfaces are interfaces that only contain only one abstract method.Some functional interfaces have been provided in the Java class library, such as Consumer, SUPPLIER, and Predicate. 2. Functional interface Functional interface is the basis for functional programming in the Java library.The function interface contains only one abstract method, and the @FunctionalInterface annotation is marked.Here are some commonly used functional interfaces: 1. Consumer interface: Receive a parameter and perform certain operations without returning values. Example code: Consumer<String> printUpperCase = (str) -> System.out.println(str.toUpperCase()); PrintupPercase.accept ("Hello, World"); // 输 2. Supplier interface: Do not receive parameters, provide a return value. Example code: Supplier<Double> randomNumber = () -> Math.random(); System.out.println (randomnumber.get ()); // Output random number 3. Predicate interface: Receive a parameter to judge and return a Boolean value. Example code: Predicate<Integer> isEven = (num) -> num % 2 == 0; System.out.println (iseven.test (4)); // Output: true: true Third, the characteristics of functional programming The functional programming paradigm has the following features in the Java library: 1. Immutability: The data in functional programming is immutable, and once it is created, it cannot be modified.This helps reduce competitive conditions in the concurrent environment. 2. Pure Functions: Pure function refers to a function without side effects, that is, the same input always generates the same output.Pure functions do not change the external state, so it is easier to test and reasonable. 3. Higher-Order Function: High-level functions refer to functions that can accept functions as parameters or return functions.The Stream API in the Java Class Library is a typical high -end function application that can perform streaming operations on the collection. 4. Application of functional programming Formulas for functional programming have a variety of application scenarios in the Java library, such as: 1. Collective operation: The Stream API in the Java class library provides a series of functional operations, such as Map, Filter, Reduce, etc., which can be functional for the collection. 2. parallel processing: The characteristics of functional programming make parallel processing easier. The STREAM API can use multi -core processors for parallel calculation. 3. Asynchronous programming: The CompletableFuture class in the Java class library supports functional programming. It can use functional interface to write asynchronous code to simplify the writing of hell. Summarize The introduction of functional programming paradigms in the Java class library makes the code more concise, easy to read and maintain.Through the support of Lambda expressions and functional interfaces, Java developers can make full use of the characteristics of functional programming to improve the abstraction and scalability of the code.When using the Java library, we can more tend to function in functional programming to improve code quality and development efficiency.