On Wed, 1 Oct 2008, Mike Schilling wrote:
Chris wrote:
Is there any way to force a class that implements an interface
to
implement both equals() and hashCode()?
I want all classes that implement a certain interface to work
properly in a HashMap. This means they need to implement their
own
version of equals() and hashCode(). Trouble is, if I add those
methods to the interface, the system doesn't squawk if the class
doesn't implement them, because it just inherits them from
Object.
I'm not sure what you're getting at, since the default versions
of
equals() and hashCode() work fine in HashMaps.
class AccountIdentity {
private int accountNumber ;
private int sortCode ;
public AccountIdentity(int accountNumber, int sortCode) {
this.accountNumber = accountNumber ;
this.sortCode = sortCode ;
}
}
class Account {
}
Map<AccountIdentity, Account> accounts = new
HashMap<AccountIdentity,
Account>() ; int acNo = 34509871 ;
int sort = 89273 ;
accounts.put(new AccountIdentity(acNo, sort), new Account()) ;
Account acc = accounts.get(new AccountIdentity(acNo, sort)) ;
assert acc != null ;