best way to check whether a character is uppercase?

[Sean Gildea]

What is the best way to check whether a string is uppercase?

I need to convert this string "thisMethodNeedsToBeParsed"
into "this method needs to be parsed"

can anyone think of the fastest / best way to do it?

thanks in advance!

[marc weber]

Offhand, I can't think of anything clever. But you can always go char by char...

class StringBreaker {
  static String breakIt(String input) {
    StringBuffer buff = new StringBuffer();
    for(int x = 0; x < input.length(); x++) {
      char c = input.charAt(x);
      if(Character.isUpperCase(c)) {
        buff.append(" " + Character.toLowerCase(c));
      }
      else {
        buff.append(c);
      }
    }
    return buff.toString();
  }
 
  public static void main(String[] args) {
    String input = "thisMethodNeedsToBeParsed";
    System.out.println("input: " + input);
    System.out.println("output: " + breakIt(input));
  }
}

[ August 08, 2005: Message edited by: marc weber ]

[Kuldeep Vaishnav]

another way is to see if the character is upper case by comparing its ascii value.

Top of my head some rough algo..............
--------------------------------------------
for(var i=0;i till length of string;i++)
var char = charOfString(i);
var asciiVal = ASCII(char);
var resultinString;
if(asciiVal between 65 to 90)
add "" and char to resultinString
else
add char to resultingString
for end
---------------------------------------------

[Timmy Marks]

if(asciiVal between 65 to 90)

Of course, this fails when using non-ascii character sets. There is a way that uses the same concept. Given that most character sets have the upper case letters consecutively, you can just ask

public String parse (String s){
  StringBuffer sb = new StringBuffer();
  char c;
  for (int i = 0; i < s.length(); i++){
    c = s.charAt(i)
    if (c >= 'A' && c <= 'Z'){
      //Character is upper case
    } else {
      //Character is not upper case
    }
  }
  return sb.toString();
}

[Ilja Preuss]

Originally posted by Timmy Marks:
Of course, this fails when using non-ascii character sets.

True.

There is a way that uses the same concept. Given that most character sets have the upper case letters consecutively, you can just ask

Well, of course we know that Java always uses unicode, which has a lot more uppercase characters then just A-Z. So in Java, your solution fails, too.

Anyway, why reinvent the wheel if Sun already did all the work for you?

[Ulf Dittmer]

What is the best way to check whether a string is uppercase?

For this part the Simplest might be "if (str.equals(str.toUpperCase())) ..."

[Alan Moore]

String str = "thisMethodNeedsToBeParsed";
str = str.replaceAll("[A-Z]", " $0").toLowerCase();

We can't know what the best way is without a lot more context, but this way seems to require the least typing.

[Ilja Preuss]

String str = "thisMethodNeedsToBeParsed";
str = str.replaceAll("[A-Z]", " $0").toLowerCase();

We can't know what the best way is without a lot more context, but this way seems to require the least typing.[/qb]<hr></blockquote>

Or even better (because it also applies to uppercase letters outside the A-Z block):

str = str.replaceAll("\\p{Lu}", " \\0").toLowerCase();

(I'm not sure that "$0" actually works - JavaDoc only seems to mention "\0"...)

[sorry for the german that somehow slipped in...]
[ August 10, 2005: Message edited by: Ilja Preuss ]

[marc weber]

Originally posted by Alan Moore:
... " $0" ...

Very nice! That's the "clever" approach I suspected was possible, but I'm not up enough on regex to come up with that myself.

I've been looking at the Pattern class API, but I can't figure out how this works. How does $0 (or \\0) translate to the matched character?
[ August 09, 2005: Message edited by: marc weber ]

[Alan Moore]

When used in the replacement string, "$0" is replaced by whatever was matched by the regex. In this case, the regex only matches one character, so that's what gets inserted. This mechanism is described in the javadoc for the appendReplacement() method of the Matcher class:

http://java.sun.com/j2se/1.5.0/docs/api/java/util/regex/Matcher.html

[marc weber]

Thanks, Alan!

I didn't realize that String's replaceAll(String regex, String replacement) method could "pass" information from the regex matcher to the replacement String. Very interesting...