java switch-case

錯誤：case expressions must be constant expressions
原因：因為case必須是常數，不能是變數

ex：
(X錯)

int E=1;
switch (col) {
 case E:
  //do something
 break;
}


(O正確)
final int E=1;
switch (col) {
 case E:
  //do something
 break;
}

(O正確)

switch (col) {
 case 1:
  //do something
 break;
}


(O正確)

switch (col) {
 case 'A':
  //do something
 break;
}