【Kotlin】Kotlin笔记5-面向对象编程3(数据类,单例类)

待我称王封你为后i 2022-11-16 04:56 184阅读 0赞

### Kotlin笔记5-面向对象编程3-数据类,单例类 ###

**3.3 面向对象编程3**

*  **数据类**

*Java实现数据类*

public class Cellphone {
    	String brand;
    	double price;
    
    	public Cellphone(String brand, double price){
    		this.brand = brand;
    		this.price = price;
    	}
    
    	@Override
    	public boolean equals(Object object){
    		return brand.hasCode() + (int) price;
    	}
    	
    	@Override
    	public String toString(){
    		return "Cellphone(brand=" + brand + ", price=" + price + ")";
    	}
    }

*Kotlin数据类*

> **data**

data class Cellphone(val brand: String, val price: Double)

fun main() {
        val cellphone = Cellphone("xiaomi", 4399.0)
        val cellphone2 = Cellphone("xiaomi", 4399.0)
        println(cellphone)
        println("cellphone equals cellphone2 " + (cellphone == cellphone2))
    }

![在这里插入图片描述][20210406131536783.png]

--------------------

*  **单例类**

*常见Java写法*

class Singleton {
        private static Singleton instance;
    
        private Singleton(){}
    
        public synchronized static Singleton getInstance(){
            if(instance==null){
                instance=new Singleton();
            }
            return instance;
        }
    
        public void singletonTest(){
            System.out.println("singletonTest is called");
        }
    }

`调用:`

Singleton singleton = Singleton.getInstance();
    singleton.singletonTest();

*Kotlin单例类*

> **object**

object Singleton {
    	fun singletonTest() {
    		println("singletonTest is called.")
    	}
    }

`调用:`

Singleton.singletonTest()

[20210406131536783.png]: /images/20221022/3b98c8af562f4582acaf37b1e00f8453.png