hi guys i need to increase the size of the font in between eg: 83.507 is my text and i need to increase the size of 50 only and all other remains the same help me guys.....

The Graphics class has a setFont method. Call it with the required font size before drawing the String that you want at that font size.
For the String: "83." and the String "50" and the String "7"

thanks and i want it to be a single string with different font sizes and is it possible and if no prob any hints would be more helpful thanks in advance.

class string offers method substring(int beginIndex, int endIndex) that highlights the characters within that string.
its not much but it might be a good way to start.

You will have to set the font size for each String that you draw. That font will be used until another setFont() call is made.