本文采用与 Java 语法作对比的方式罗列并介绍** Kotlin 的函数用法**。依然是类似《Kotlin 带你飞 • 语法篇 • 基础》的套路，希望能对看到这篇文章的您有所帮助吧。
相关文章：
《Kotlin 带你飞》
《Kotlin 带你飞 • 语法篇 • 基础》
《Kotlin 带你飞 • 实战篇》
相关 Github 源码
版权声明：本文为 frendy 原创文章，可以随意转载，但请务必在明确位置注明出处。
Basic Function
Java
public void hello() {
System.out.print("Hello World!");
}
Kotlin
fun hello() {
println("Hello World!")
}
Arguments
Java
public void hello(String name){
System.out.print("Hello " + name + "!");
}
Kotlin
fun hello(name: String) {
println("Hello $name!")
}
Default Values
Java
public void hello(String name) {
if (name == null) {
name = "World";
}
System.out.print("Hello " + name + "!");
}
Kotlin
fun hello(name: String = "World") {
println("Hello $name!")
}
Return
Java
public boolean hasItems() {
return true;
}
Kotlin
fun hasItems() : Boolean {
return true
}
Single-Expression
Java
public double cube(double x) {
return x * x * x;
}
Kotlin
fun cube(x: Double) : Double = x * x * x
Vararg
Java
public int sum(int... numbers) { }
Kotlin
fun sum(vararg x: Int) { }
Main
Java
public class MyClass {
public static void main(String[] args) { }
}
Kotlin
fun main(args: Array<String>) { }
Named Arguments
Java
public static void main(String[]args){
openFile("file.txt", true);
}
public static File openFile(String filename, boolean readOnly) { }
Kotlin
fun main(args: Array<String>) {
openFile("file.txt", readOnly = true)
}
fun openFile(filename: String, readOnly: Boolean) : File { }
Optional Arguments
Java
public static void main(String[]args){
createFile("file.txt");
createFile("file.txt", true);
createFile("file.txt", true, false);
createExecutableFile("file.txt");
}
public static File createFile(String filename) { }
public static File createFile(String filename, boolean appendDate) { }
public static File createFile(String filename, boolean appendDate, boolean executable) { }
public static File createExecutableFile(String filename) { }
Kotlin
fun main(args: Array<String>) {
createFile("file.txt")
createFile("file.txt", true)
createFile("file.txt", appendDate = true)
createFile("file.txt", true, false)
createFile("file.txt", appendDate = true, executable = true)
createFile("file.txt", executable = true)
}
fun createFile(filename: String, appendDate: Boolean = false, executable: Boolean = false): File { }
Generic Methods
Java
public void init() {
List<String> moduleInferred = createList("net");
}
public <T> List<T> createList(T item) { }
Kotlin
fun init() {
val module = createList<String>("net")
val moduleInferred = createList("net")
}
fun <T> createList(item: T): List<T> { }
Data Classes - Destructuring
Java
public static void main(String[]args) {
Book book = createBook();
System.out.println(book);
System.out.println("Title: " + book.title);
}
public static Book createBook(){
return new Book("title_01", "author_01");
}
public class Book {
final private String title;
final private String author;
public Book(String title, String author) {
this.title = title;
this.author = author;
}
public String getTitle() {
return title;
}
public String getAuthor() {
return author;
}
@Override
public String toString() {
return "Title: " + title + " Author: " + author;
}
}
Kotlin
fun main(args: Array<String>) {
val book = createBook();
// or
val (title, author) = createBook()
println(book)
println("Title: $title")
}
fun createBook() : Book{
return Book("title_01", "author_01")
}
data class Book(val title: String, val author: String)
愿大家都能飞得更高、飞得更开心...嗯，开心很重要...
qrcode_card.png
