Assert 在Java和Groovy中的区别

对于防御性编程而言，assert一直都是非常重要的工具。但对于熟悉-ea参数的Java程序员而言，当他们看到所有Groovy断言无论是否有-ea都照样执行时一定会非常困惑。
事实上，Groovy的断言是无条件开启的！
对此，开发人员Roshan Dawrani做了如下解释：（原文）
The JDK documentation has a long chapter on assertions that talks about the disabling feature for assertions and its impact on compiling, starting the VM, and resulting design issues. Although this is fine and the design rationale behind Java assertions is clear, we feel the disabling feature is the
biggest stumbling block for using assertions in Java. You can never be sure that your assertions are really executed.
在Core Java（或者是TIJ？记不清了）里，作者提到assertion类似“在海边开赛艇要带好你的卡通救生圈；如果船已经在大海中央，就把救生圈扔掉好了”。不过，在Groovy中，显然这种防御措施会一直跟随你到大海的任意角落（希望不是海底）。
PS：如果仔细看看Groovy断言的输出，你一定会意识到它对于debug是多么有用：
1: def xml = new XmlParser().parseText("x")
2: assert "y" == xml.text()
3: -----
4: output:
5:
6: assert "y" == xml.text()
7: | | |
8: | | x
9: | test[attributes={}; value=[x]]
10: false
11:
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Quote of the day:
I didn't really say everything I said. - Yogi Berra