第139題

Given a method that must ensure that its parameter is not null:
11. public void someMethod(Object value){
12. //check for null value
...
20. System.out.println(value.getClass());
21. }

What, inserted at line 12, is the appropriate way to handle a null value?

A. assert value == null;
B. assert value != null : "value is null";
C. if (value == null){
throw new AssertionException("value is null");
}
D. if (value == null){
throw new IllegalArgumentException("value is null");
}

答案：D
參考：9-3 使用throw自行產生例外事件、9-7 測試程式與AssertionError錯誤事件
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第12行中加code處理空值的情況
D. if (value == null){ //先檢查是否為空值
throw new IllegalArgumentException("value is null"); //為空值時再產生Exception
}