1 匿名类
1）无继承
fun main() {
var obj = object {
var name: String = "zhang"
override fun toString(): String {
return name
}
}
println(obj) // zhang
}
2）有继承
fun main() {
var obj = object: People {
var name: String = "zhang"
override fun play() {
println("play, $name")
}
}
obj.play() // play, zhang
}
interface People {
fun play()
}
2 单例
2.1 案例一
1）object 单例
fun main() {
var singleton = Singleton
println(singleton)
}
object Singleton {
var name = "zhang"
override fun toString(): String {
return return name
}
}
2）对应的 java 类
Singleton.java
public final class Singleton {
private static String name;
public static final Singleton INSTANCE;
static {
INSTANCE = new Singleton();
name = "zhang";
}
private Singleton() {
}
public final String getName() {
return name;
}
public final void setName(String var1) {
name = var1;
}
public String toString() {
return name;
}
}
java 中调用如下。
Singleton singleton = Singleton.INSTANCE;
System.out.println(singleton);
2.2 案例二
1）object 单例
fun main() {
var stu = Student.Tools.create("zhang")
println(stu) // zhang
println(Student.Tools.age) // 15
}
class Student(var name: String) {
object Tools {
var age: Int = 15
fun create(name: String): Student {
return Student(name)
}
}
override fun toString(): String {
return name
}
}
2）对应的 java 类
Student.java
public final class Student {
private String name;
public Student(String name) {
this.name = name;
}
public final String getName() {
return this.name;
}
public final void setName(String var1) {
this.name = var1;
}
public String toString() {
return this.name;
}
public static final class Tools {
private static int age;
public static final Tools INSTANCE;
static {
INSTANCE = new Tools();
age = 15;
}
private Tools() {
}
public final Student create(String name) {
return new Student(name);
}
public final int getAge() {
return age;
}
public final void setAge(int var1) {
age = var1;
}
}
}
java 中调用如下。
Student stu = Student.Tools.INSTANCE.create("zhang");
System.out.println(stu);
System.out.println(Student.Tools.INSTANCE.getAge());
3 伴生类
3.1 伴生类应用
1）应用
fun main() {
var stu = Student.create("zhang")
println(stu) // zhang
println(Student.age) // 15
}
class Student(var name: String) {
companion object Tools {
var age: Int = 15
fun create(name: String): Student {
return Student(name)
}
}
override fun toString(): String {
return name
}
}
2）反编译后 java 类
Student.java
public final class Student {
private String name;
private static int age = 15;
public static final Tools Tools = new Tools(();
public Student(String name) {
this.name = name;
}
public final String getName() {
return this.name;
}
public final void setName(String var1) {
this.name = var1;
}
public String toString() {
return this.name;
}
public static final class Tools {
private Tools() {
}
public final Student create(String name) {
return new Student(name);
}
public final int getAge() {
return Student.age;
}
public final void setAge(int var1) {
Student.age = var1;
}
}
}
java 中调用如下。
Student stu = Student.Tools.create("zhang");
System.out.println(stu);
System.out.println(Student.Tools.getAge());
3.2 @JvmStatic 应用
为方便 Java 中也可以直接调用 Student.create()，可以给伴生类中的函数添加 @JvmStatic 注解。
1）应用
class Student(var name: String) {
companion object Tools {
var age: Int = 15
@JvmStatic
fun create(name: String): Student {
return Student(name)
}
}
override fun toString(): String {
return name
}
}
java 中调用如下。
Student stu = Student.create("zhang");
System.out.println(stu);
System.out.println(Student.Tools.getAge());
2）反编译后 java 类
public final class Student {
private String name;
private static int age = 15;
public static final Tools Tools = new Tools();
public Student(String name) {
this.name = name;
}
public static final Student create(String name) {
return Tools.create(name);
}
public final String getName() {
return this.name;
}
public final void setName(String var1) {
this.name = var1;
}
public String toString() {
return this.name;
}
public static final class Tools {
private Tools() {
}
public final Student create(String name) {
return new Student(name);
}
public final int getAge() {
return Student.age;
}
public final void setAge(int var1) {
Student.age = var1;
}
}
}
说明：对比有无 @JvmStatic 注解反编译后的代码，发现有 @JvmStatic 注解时，反编译的代码里 Student 类中多了静态的 create 方法，因此在 Java 中可以直接调用 Student.create()。
声明：本文转自【Kotlin】匿名类和伴生类。
