Groovy def和Java对象之间的区别？ [英] Difference between Groovy def and Java Object?

问题描述

Groovy：

  def name =stephanie
  

Java：

 对象名称=stephanie
  

因为两者似乎都充当了与它们交互的对象，因此我必须将它们转换为其原始的预期类型。

我最初是在寻找一个java等价物C＃的动态类（ Java相当于C＃动态类类型？）和有人建议看看Groovy的 def

例如我对groovy的def的印象是我可以做以下：

  def DOB = new Date（1998,5,23）; 
 int x = DOB.getYear（）; 
  

但是这不会建立

steph

解决方案编辑：
我发现错误是因为我有一个使用def定义的公共属性的Groovy类（在我的示例中为DOB）然后试图从.java类访问它们（在我上面的示例中调用.getYear（））。它是一个新手的错误，但问题是一旦对象离开了Groovy文件，它就被当作对象。感谢您的帮助！

解决方案

本身，这两种说法没有太大的区别。但由于Groovy是一种动态语言，因此您可以编写

  def name =Stephanie
 println name.toUpperCase ）//不需要强制转换
  

您需要在Java版本中进行明确的转换

 对象名称=Stephanie; 
 System.out.println（（（String）name）.toUpperCase（））; 
  

因此， def 使得更多在Groovy中感觉比在Java中使用 Object 没有根据。

I'm trying to figure out the difference between

Groovy:

def name = "stephanie"

Java:

Object name = "stephanie"

as both seem to act as objects in that to interact with them i have to cast them to their original intended type.

I was originally on a search for a java equivalent of C#'s dynamic class ( Java equivalent to C# dynamic class type? ) and it was suggested to look at Groovy's def

for example my impression of groovy's def is that I could do the following:

def DOB = new Date(1998,5,23);
int x = DOB.getYear();

however this wont build

thanks,steph

Solution edit: Turns out the mistake iw as making is I had a groovy class wtih public properties (in my example above DOB) defined with def but then was attemping to access them from a .java class(in my example above calling .getYear() on it). Its a rookie mistake but the problem is once the object leaves a Groovy file it is simply treated as a Object. Thanks for all your help!

解决方案

Per se, there is not much difference between those two statements; but since Groovy is a dynamic language, you can write

def name = "Stephanie"
println name.toUpperCase() // no cast required

while you would need an explicit cast in the Java version

Object name = "Stephanie";
System.out.println(((String) name).toUpperCase());

For that reason, def makes much more sense in Groovy than unfounded use of Object in Java.

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