构造函数

Java

final File file = new File("file.txt");

Kotlin

val file = File("file.txt")

类

Java

public final class User {
}

Kotlin

class User

公开类

Java

public class User {
}

Kotlin

open class User

属性类

Java

final class User {private final String name;public User(String name) {this.name = name;}public String getName() {return name;}}

Kotlin

class User(val name: String)

有参数的构造函数

Java

final class User {private String name;public User(String name) {this.name = name;}public String getName() {return name;}public void setName(String name) {this.name = name;}}

Kotlin

class User(var name: String)

构造函数中的可选参数

Java

final class User {private String name;private String lastName;public User(String name) {this(name, "");}public User(String name, String lastName) {this.name = name;this.lastName = lastName;}// And Getters & Setters}

Kotlin

class User(var name: String, var lastName: String = "")

对类中参数赋值

Java

public class Document {private String id = "00x";public String getId() {return id;}public void setId(String id) {if(id != null && !id.isEmpty()) {this.id = id;}}}

Kotlin

class Document{var id : String = "00x"set(value) {if(value.isNotEmpty())  field = value}
}

抽象类

Java

public abstract class Document{public abstract int calculateSize();
}public class Photo extends Document{@Overridepublic int calculateSize() {}
}

Kotlin

abstract class Document {abstract fun calculateSize(): Int
}class Photo : Document() {override fun calculateSize(): Int {}
}

单例类

Java

public class Document {private static final Document INSTANCE = new Document();public static Document getInstance(){return INSTANCE;}}

Kotlin

object Document {}

扩展类

Java

public class ByteArrayUtils {public static String toHexString(byte[] data) {}}final byte[] dummyData = new byte[10];final String hexValue = ByteArrayUtils.toHexString(dummyData);

Kotlin

fun ByteArray.toHex() : String {}val dummyData = byteArrayOf()
val hexValue = dummyData.toHex()

内部类

Java

public class Documment {class InnerClass {}}

Kotlin

class Document {inner class InnerClass
}

嵌套类

Java

public class Documment {public static class InnerClass {}}

Kotlin

class Document {class InnerClass}

接口

Java

public interface Printable {void print();
}public class Document implements Printable {@Overridepublic void print() {}
}

Kotlin

interface Printable{fun print()
}class Document : Printable{override fun print() {}
}