How to compare one character from a string with another string [duplicate]

Answer 1

Use .equals() to compare strings. When you use == i think it checks if they both reference same thing or not.

hope that helps. :)

Answer 2

Change your string to char. char current = hex.charAt(i);

Then in your else if you need to check for 'b' and 'B'

else if (current == 'b' || current == 'B') { }

Answer 3

Actually, there is a very simple and elegant way of doing it:

int result = Integer.parseInt(hex, 16);

Answer 4

You need to compare strings with equals method

else if ("b".equals(current)) 

you can find more details here: http://www.javabeginner.com/learn-java/java-string-comparison

Answer 5

Try initializing a char to the char value returned by charAt()

char current = hex.charAt(i);

Then in your conditional use the literal char:

else if (current == 'b') 

Since char is a primitive you can compare it using the == operator. In the former code you were comparing a String using ==, since a String is an Object the code is checking to see if they are the same Object not if they have the same value as the String.equals() method would.

Answer 6

Without the full code it is difficult to be certain, but the "for input string: xx" form is usually the message associated with NumberFormatException. Are you converting (part of) the string to a number by using Integer.valueOf(), Integer.parseInt() or similar methods by chance?

If this is the case in order to have them accept an hexadecimal digit (a-f) you need to explicitly state you are passing in a 16-base digit, by calling the methods that accept a second parameter for the radix - e.g. Integer.valueOf(string, 16).

Also, like others pointed out already, the correct way to compare strings is to use the equals method, since the == operator will only return true if the two references points to the exact same object, regardless of its value (content).