indexOf返回值問題

  

String s  = "aoood";
System.out.println(s.indexOf(""));//返回0
System.out.println(s.indexOf("w"));//返回-1
 
 
例如
var customerKinds="GR,QY";
（customerKinds.indexOf(customerKind）!= -1){
    --------------------------------------------------------------
}
customerKind="''" 則會全部顯示       customerKind有值，則會根據值顯示