Kotlin 带你飞 • 语法篇 • 类

本文采用与 Java 语法作对比的方式罗列并介绍 Kotlin 类的用法。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 • 语法篇 • 函数》

《Kotlin 带你飞 • 实战篇》

相关 Github 源码


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Constructor Call

Java

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

Kotlin

val file = File("file.txt")

---

Class

Java

public final class User {  }

Kotlin

class User

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Open Class

Java

public class User {  }

Kotlin

open class User

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Final Attributes

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)

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Primary Constructor

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)

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Optional Arguments in Constructors

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 = "")

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Properties

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
        }
}

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Abstract Class

Java

public abstract class Document{
   public abstract int calculateSize();
}

public class Photo extends Document{
    @Override
    public int calculateSize() {

    }
}

Kotlin

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

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

    }
}

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Singleton

Java

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

    public static Document getInstance(){
       return INSTANCE;
    }
}

Kotlin

object Document {

}

---

Extensions

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()

---

Inner Class

Java

public class Documment {
    class InnerClass {

    }
}

Kotlin

class Document {
    inner class InnerClass
}

---

Nested Class

Java

public class Documment {
    public static class InnerClass {

    }
}

Kotlin

class Document {
    class InnerClass
}

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Interface

Java

public interface Printable {
    void print();
}

public class Document implements Printable {
    @Override
    public void print() {

    }
}

Kotlin

interface Printable{
    fun print()
}

class Document : Printable {
    override fun print() {

    }
}

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愿大家都能飞得更高、飞得更开心...嗯，开心很重要...

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