Looping in a String to find Unicode characters is taking too much time

I am creating a custom field where I want to replace some unicode caracters by pictures. Its like doing emoticons for blackberry device. Well I have a problem looping the caracters in the edit field and replacing the unicode caracters by images. When the text becomes too long, the loop takes too much time.

My code is as follows:

String aabb = "";
char[] chara = this.getText().toCharArray();
for (int i = loc; i < chara.length; i ++) {
   Character 开发者_如何学Ccc = new Character(chara[i]);
   aabb += cc.toString();
   if (unicodeCaracter) {
       //Get the location
       //draw the image in the appropriate X and Y
   }
}

Well this works fine, and the images are getting in the right place. But the problem is when the text becomes large, the looping is taking too much time, and the input of the text on the device becomes non friendly.

How to find the unicode caracters in a text without having to loop each time for them? Is their another way than this that I missed?

I need help with this issue. Thanks in advance

Well you're creating a new Character and a new String in each iteration of the loop, and converting the string to a character array to start with. You're also using string concatenation in a loop rather than using a StringBuffer. All of these will be hurting performance.

It's not obvious what you mean by "Unicode characters" here - all characters in Java are Unicode characters. I suspect you really want something like:

String text = this.getText();
StringBuffer buffer = new StringBuffer(text.length());
for (int i = 0; i < text.length(); i++) {
    char c = text.charAt(i);
    buffer.append(c);
    if (c > 127) { // Or whatever
        // Take some action
    }
}

I'm assuming the "take some action" will be changing the buffer in some respect, otherwise the buffer is pointless of course... but fundamentally that's likely to be the sort of change you want.

The string concatenation in a loop is a particularly bad idea - see my article on it for more details.

What takes time is the string concatenation.

Strings are immutable in Java. Each time you do

aabb += cc.toString();

you create a new String object containing all the chars of the previous one, which must be garbage collected, plus the new ones. Use a StringBuilder to build your string:

StringBuilder builder = new StringBuilder(this.getText().length() + 100); // size estimation
char[] chara = this.getText().toCharArray();
for (int i = loc; i < chara.length; i++) {
   builder.append(chara[i]);
   if (unicodeCaracter) {
       //Get the location
       //draw the image in the appropriate X and Y
   }
}
String aabb = builder.toString();

Well, besides speeding up your loop, you could also try and minimize the work load.

If the user is appending text you could store the last position you scanned previously time and start from there..

On inserts/deletes you'd need to get the caret position and scan the deleted/inserted part and maybe surrounding characters (if you have character groups instead of single characters that get replaced).

However, fixing loop performance is likely to give you a better improvement in your case, as I doubt you'll have that long strings to make that algorithmic change worthwhile.

The most important performance enhancements have already been stated but looping backwards will also help in BlackBerry apps.

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