[OCPJP]Properties的用法

Given the content of /resourses/Message.properties:

and given the code fragment:

Properties prop = new Properties();
FileInputStream fis = new FileInputStream("/resources/Message.properties");
prop.load(fis);
System.out.println(prop.getProperty("welcome1"));
System.out.println(prop.getProperty("welcome2", "Test"));//line n1
System.out.println(prop.getProperty("welcome3"));

What is the result?

A.

followed by an Exception stack trace
B.

followed by an Exception stack trace
C.

D. A compilation error occurs at line n1.

題解

程式第13行，會輸出「/resourses/Message.properties」中「welcome1」鍵值所對應的值，即為「Good day!」。

程式第14行，由於「/resourses/Message.properties」中不存在「welcome2」鍵值，但有設定預設值「Test」，所以會輸出預設值「Test」。

程式第15行，由於「/resourses/Message.properties」中不存在「welcome3」鍵值，所以輸出「null」。