[OCPJP]Properties的用法

Given the content of /resourses/Message.properties:

welcome1="Good day!"

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"));

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?

Good day!
Test

followed by an Exception stack trace
B.

Good day!

followed by an Exception stack trace
C.

Good day!
Test
null

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」。

MagicLen

[OCPJP]Properties的用法

題解

關於作者

Magic Len

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