What does "Enter" return?
I am trying to allow the user to just press "Enter" to return to the main menu of my class. But when I test it in the if statement it never gives me true. What am I doing wrong?
Here is the code section :
String ext =null;
System.out.print("Please enter extension or Enter to return to Main menu: ");
ext = (kr.readLine());
;
if (!ext.equalsIgnoreCase(null) ){System.out.println("I'm in here");
fb.currentMask =(ext);
fb.getFiles(ext);
}
So far I have tried testing ext against null, "" and " " .
Also I've tried using equals, equalsIgnoreCase, and ==.
[831 byte] By [
Palmera] at [2007-10-2 6:50:07]
test against "", not null
whatever.equals(null) (including equalsIgnoreCase(null)) can never be true in Java.
Null and the empty string ("") are not the same.
String s1 = null; // s1 is a reference that doesn't point to any object
String s2 = ""; // s2 is a reference that points to a String object that has no characters
System.out.println(s1 == null); // true
System.out.println(s2 == null); // false
System.out.pirntln(s1.equals(null)); // NullPointerException
System.out.println(s2.equals(null)); // false
System.out.pirntln(s1.equals(s2)); // NullPointerException
System.out.println(s2.equals(s1)); // false
jverda at 2007-7-16 13:59:03 >
> test against "", not null
I tried the following:
String ext = null;
System.out.print("Please enter extension or Enter to return to Main menu: ");
ext = (kr.readLine());
;
if (!ext.equalsIgnoreCase("") ){System.out.println("I'm in here");
fb.currentMask =(ext);
fb.getFiles(ext);
}
If this looks right, is there something else that would cause the "if" to never return truel.
We don't actually know what the "kr" variable is. If it's a BufferedReader then it would trim off line-ending characters. But maybe it's something else that leaves the line-ending characters alone, and you're getting them.
Why don't you just look at the contents of ext instead of inviting us to speculate? If you don't have a debugger thenSystem.out.println(ext);
System.out.println(ext.length());
System.out.println("" + ext + "");
are all good choices. Guessing is a slow process.
seems like another option would beext.length()>0
> We don't actually know what the "kr" variable is. If
> it's a BufferedReader then it would trim off
> line-ending characters. But maybe it's something else
> that leaves the line-ending characters alone, and
> you're getting them.
>
> Why don't you just look at the contents of ext
> instead of inviting us to speculate? If you don't
> have a debugger thenSystem.out.println(ext);
> System.out.println(ext.length());
> System.out.println("" + ext + "");
are
> all good choices. Guessing is a slow process.
I put in the code you suggested and found that when Enter was pressed then ext was printing out the line:
Please enter extension or Enter to return to Main menu:
I have been using this KeyboardReader our instructor gave us and when I opened it up to look, it is a bufferedReader.
I can fix the problem if I use a println before the readLine instead of using print before the readLine. I don't know why this works. The readLine works when anything but "" is entered by the user. Is there a way to use the print statement?
