in your findclient method, try somthing like this:
public void findclient(String details)
{
for(int x=0; x<arraySize; x++) {
//I donno how your Client class is defined, but you'll need a method that
//returns the name
if( (collection[x].getName()).equalsIgnoreCase(details)) {
//Found it! do whatever you want here.
}
}
}
if you want that method to return some data found in there, i'd make sure you search the whole array and put the found entries on a new array, and return THAT, as names have a nasty habit of being non-unique, and just returning the first one you find could leave out a lot of data.