这篇文章主要介绍“Kotlin与Java的异同点有哪些”,在日常操作中,相信很多人在Kotlin与Java的异同点有哪些问题上存在疑惑,小编查阅了各式资料,整理出简单好用的操作方法,希望对大家解答”Kotlin与Java的异同点有哪些”的疑惑有所帮助!接下来,请跟着小编一起来学习吧!
打印日志
Java
System.out.print("hello world");System.out.println("hello world");
Kotlin
print("hello world")println("hello world")
定义变量与常量常
Java
String name =
"hello world";final String name =
"hello world";
Kotlin
var name =
"hello world"val name =
"hello world"
null声明
Java
String otherName;otherName =
null;
Kotlin
var otherName :
String?otherName =
null
空判断
Java
if (text !=
null) { int length = text.length();}
Kotlin
text?.let { val length = text.length}// or simplyval length = text?.length
字符串拼接
Java
String firstName =
"Android";String lastName =
"Architect";String message =
"My name is: " + firstName +
" " +
lastName;
Kotlin
val firstName =
"Android"val lastName =
"Architect"val message =
"My name is:
$firstName $lastName"
换行
Java
String text =
"First Line\n" + "Second Line\n" + "Third Line";
Kotlin
val text =
""" |First Line |Second Line |Third Line """.trimMargin()
三元表达式
Java
String text = x >
5 ?
"x > 5" :
"x <= 5";
Kotlin
val text =
if (x >
5) "x > 5"
else "x <= 5"
操作符
java
final int andResult = a & b;final int orResult = a | b;final int xorResult = a ^ b;final int rightShift = a >>
2;final int leftShift = a <<
2;final int unsignedRightShift = a >>>
2;
Kotlin
val andResult = a and bval orResult = a or bval xorResult = a xor bval rightShift = a shr
2val leftShift = a shl
2val unsignedRightShift = a ushr
2
类型判断和转换 (声明式)
Java
Car car = (Car)
object;
Kotlin
var car =
object as Car
类型判断和转换 (隐式)
Java
if (object instanceof Car) { Car car = (Car)
object;}
Kotlin
if (object is Car) {
var car =
object // 自动识别}
多重条件
Java
if (score >= 0 && score <= 300) { }
Kotlin
if (score in 0..300) { }
更灵活的case语句
Java
int score =
// some score;String grade;switch (score) { case 10: case 9: grade =
"Excellent"; break; case 8: case 7: case 6: grade =
"Good"; break; case 5: case 4: grade =
"OK"; break; case 3: case 2: case 1: grade =
"Fail"; break; default: grade =
"Fail";}
Kotlin
var score =
// some scorevar grade =
when (score) { 9,
10 ->
"Excellent" in 6..8 ->
"Good" 4,
5 ->
"OK" in 1..3 ->
"Fail" else ->
"Fail"}
for循环
Java
for (int i = 1; i <= 10 ; i++) { }for (int i = 1; i < 10 ; i++) { }for (int i = 10; i >= 0 ; i--) { }for (int i = 1; i <= 10 ; i+=2) { }for (int i = 10; i >= 0 ; i-=2) { }for (String item : collection) { }for (Map.Entry<String, String> entry: map.entrySet()) { }
Kotlin
for (i in 1..10) { }for (i in 1 until 10) { }for (i in 10 downTo 0) { }for (i in 1..10 step 2) { }for (i in 10 downTo 0 step 2) { }for (item in collection) { }for ((key, value) in map) { }
更方便的集合操作
Java
final List<Integer> listOfNumber = Arrays.asList(1,
2,
3,
4);final Map<Integer, String> keyValue =
new HashMap<Integer, String>();map.put(1,
"Android");map.put(2,
"Ali");map.put(3,
"Mindorks");// Java 9final List<Integer> listOfNumber = List.of(1, 2, 3, 4);final Map<Integer, String> keyValue = Map.of(1, "Android", 2, "Ali", 3, "Mindorks");
Kotlin
val listOfNumber = listOf(1,
2,
3,
4)val keyValue = mapOf(1 to
"Android",
2 to
"Ali",
3 to
"Mindorks")
遍历
Java
// Java 7 and belowfor (Car car : cars) { System.out.println(car.speed);}// Java 8+cars.forEach(car -> System.out.println(car.speed));// Java 7 and belowfor (Car car : cars) { if (car.speed > 100) { System.out.println(car.speed); }}// Java 8+cars.stream().filter(car -> car.speed > 100).forEach(car -> System.out.println(car.speed));
Kotlin
cars.forEach { println(it.speed)}cars.filter { it.speed >
100 } .forEach {
println(it.speed)}
方法定义
Java
void doSomething() {
// logic here}void doSomething(int... numbers) { // logic here}
Kotlin
fun doSomething() {
// logic here}fun doSomething(vararg numbers: Int) { // logic here}
带返回值的方法
Java
int getScore() {
// logic here return score;}
Kotlin
fun getScore():
Int {
// logic here return score}// as a single-expression functionfun getScore(): Int = score
无结束符号
Java
int getScore(int value) { // logic here return 2 * value;}
Kotlin
fun getScore(value:
Int):
Int {
// logic here return 2 * value}// as a single-expression functionfun getScore(value: Int): Int = 2 * value
constructor 构造器
Java
public class Utils { private Utils() { // This utility class is not publicly instantiable } public static int getScore(int value) { return 2 * value; }}
Kotlin
class Utils private constructor() { companion object { fun getScore(value:
Int):
Int { return 2 * value } }}// another wayobject Utils { fun getScore(value: Int): Int { return 2 * value }}
Get Set 构造器
Java
public class Developer { private String name; private int age; public Developer(String name,
int age) { this.name = name; this.age = age; } public String
getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; }}
Kotlin
data class Developer(val name: String, val age: Int)
到此,关于“Kotlin与Java的异同点有哪些”的学习就结束了,希望能够解决大家的疑惑。理论与实践的搭配能更好的帮助大家学习,快去试试吧!若想继续学习更多相关知识,请继续关注亿速云网站,小编会继续努力为大家带来更多实用的文章!
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原文链接:http://blog.itpub.net/69923331/viewspace-2697120/