[Java] SCJP 例題 119

Given:
11. public static void main(String[] args){
12.   String str = "null";
13.   if (str == null) {
14.     System.out.println("null");
15.   }else (str.length() == 0) {
16.     System.outprintln("zero");
17.   }else{
18.     System.out.println("some");
19.   }
20. }


What is the result?[1]
  A. null
  B. zero
  C. some
  D. Compilation fails.
  E. An exception is thrown at runtime.

少了一個if.

[1] http://192.192.246.169/~wells/wiki/index.php/SCJP_1.6%E7%89%88%E8%80%83%E9%A1%8C_119

這不是重點啦XD

如果成是正確的, 有加上if呢?!

答案會是some, 因為String理面有字串"null", str.length() = 4.

除非你將String str="", 那答案才會是zero.

好像不會有答案跳到null, 因為str如果沒給値就放置判斷式中,

這個String沒初始化, 在編譯時就會被擋下來. 

ex_119_string_null.java:4: error: variable s might not have been initialized
                if(str == null)
                   ^
1 error

- - - - -

public class ex_119_string_null{
 public static void main(String args[]){
  String str ="";
  if(str == null)
   System.out.println("null");
  else if(str.length()==0)
   System.out.println("zero");
  else
   System.out.println("else: "+str+" "+str.length());
 }
}