find method is given like this in instruction:
// Returns an array of record numbers that match the specified
// criteria. Field n in the database file is described by
// criteria[n]. A null value in criteria[n] matches any field
// value. A non-null value in criteria[n] matches any field
// value that begins with criteria[n]. (For example, "Fred"
// matches "Fred" or "Freddy".)
public int  find(String  criteria)
Here I am talking about search from database side not from User Interface
then find method will return record number array of those records those are matches with this condition (criteria="SubContractor name" OR criteria="city")
since only criteria(sub contractor name ) and criteria(city) are specified.