Kotlin framework activity expansion initial detection: the application field of Java class library

Kotlin framework activity expansion initial detection: the application field of Java class library Introduction: Event expansion is a powerful feature of KOTLIN, which allows us to convert the existing Java class libraries and API into more concise, easy -to -use, and codes that meet Kotlin habits.This article will introduce the basic concepts of activity expansion in the Kotlin framework, and provide some application scenarios and corresponding code examples using the Java library. Overview of activity extension: Event expansion is a ability to expand existing classes by adding new functions in Kotlin.It does not need to modify or inherit the class, so it can avoid some restricted and lengthy grammar in Java.The activity extension function can be called like a member function of the class, and new behaviors can be added to the class. Use the application scenario of the Java library: 1. String operation: The activity extension provides many practical functions for the String class in KOTLIN, which can simplify the operation of the string.For example, we can use the activity extension function to determine whether the string is empty, whether it contains a specified sub -string, and can perform laxic conversion and other operations. kotlin fun String?.isNotNullOrEmpty(): Boolean { return this != null && this.isNotEmpty() } val str = "Hello World" Println (str.isnotnullorempty ()) // Output true 2. Collection operation: The activity extension function can add new features to the set class of Kotlin (such as List, SET, MAP, etc.).For example, we can sort, filter, mapping, and return to the collection, without the need to introduce an additional third -party library. kotlin val numbers = listOf(2, 5, 3, 9, 1, 4) val sortedNumbers = numbers.sorted() Println (sortednumbers) // output [1, 2, 3, 4, 5, 9] val evenNumbers = numbers.filter { it % 2 == 0 } Println (Evennumbers) // Output [2, 4] 3. IO operation: Event expansion can also provide more concise functions for the Java IO class library, simplify the code of file reading and writing and flow operation.For example, we can add a function to the file class to read the file content and return the string directly. kotlin fun File.readText(): String = inputStream().bufferedReader().use { it.readText() } val file = File("sample.txt") val content = file.readText() Println (Content) // Output file content Summarize: Event expansion is a very useful feature in KOTLIN. It can convert the functions of the Java library into a more concise, easy -to -use, and codes that meet Kotlin habits.Through activity expansion, we can add new behaviors to the class, simplify the operation of the string and collection, and simplify the IO operation.The code example of these application scenarios shows the powerful functions and flexibility of the event expansion, enabling us to use the Java class library more efficiently.