I have a java exercise follow: there are n machines of 3 type A,B,C, each machine has coordinates (x,y) and operate radius, with data get from a XML file, for instance:

<machine> <number ="1"> <type>C</type> <cox>40</cox> <coy>80</coy> <rad>30</rad> </number> <number ="2"> <type>A</type> <cox>25</cox> <coy>35</coy> <rad>40</rad> </number> <number ="3"> <type>C</type> <cox>50</cox> <coy>10</coy> <rad>50</rad> </number> </machine>

I made 3 class A, B, C and already got information from xml file. But the 2 problems is that:

1. calculate the distance between each machine

2. add them to list of each machine if distance is less than radius.

I known the formula to calculate the distance but dont know how to get x, y to calculate nx(n-1) distances, and add them to list. Could anyone give me the idea to solve these 2 problems? Thank so much!