Java 程式設計(基礎)-Wrapper

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`Wrapper詳細內容
http://www.codedata.com.tw/book/java-basic/index.php?p=ch8-1`

 

 

基本資料型態 Wrapper 類別

byte java.lang.Byte

short java.lang.Short

int java.lang.Integer

long java.lang.Long

float java.lang.Float

double java.lang.Double

char java.lang.Character

boolean java.lang.Boolean

`public class WrapperDemo {
	public static void main(String[] args) {

		//基本型態，首字大寫的話就是宣告的是物件型別的基本型態
		//基本型別，只能做強制轉型，物件型別則可以用軟性轉型
		
        Integer aa = new Integer(20);//Integer 是int的物件型態，物件型態就是要用new 來產生為主
        Double zzz= new Double(1.01);//Double 是double的物件型態，物件型態就是要用new 來產生為主
        

        System.out.print("原來的 int 值:");
        System.out.println(
                aa.intValue());//本來的int型態並列印出來
        
        System.out.print("double 型態:");
        System.out.println(
                aa.doubleValue());//轉換為Doule型態並列印出來
        
        float bb = aa.floatValue();//軟性轉換,較不會有錯誤顯示
        long cc = (long)aa;//硬性轉換，較容易有錯誤並顯示
        
        System.out.println(bb);//列印出來再java裡面 其實他是先轉換成字串
        System.out.println(cc);
	}
}`

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