How to find collision between balls in Applet animation

I'm trying to create a animation in which a bomb falls down and there is three balloon moving from left to right.
I want to know how would i come to know bomb hit ball.
I've tried to locate by making co-ordinate equals but its come out wrong.
Can you give any idea pls !!!

There are plenty of ways to do collision detection, and google is your friend here.

One way is to simply measure the distance between the Objects- if it's less than the sum of both their radii, they're colliding.