I väntan på closures

JavaForum2013019-2.java

// higher order "method" (class)
public abstract class UseSafely<T> {

    public abstract T with(AccountConnection connection);

    public T runWith(AccountConnection connection) {
        synchronized (connection) {
            try {
                connection.open();
                return with(connection);
            } catch (Exception e) { ... }
            } finally {
                connection.close();
            }
        }
    }
}


public class WhereWeUseIt() {

    // new
    public int withdraw(AccountConnection connection, final int amount) {
        return new UseSafely<Integer>() {
            @Override
            public Integer with(AccountConnection c) {
                return c.withdraw(amount);
            }
        }.runWith(connection);
    }

    // old
    public int withdraw(AccountConnection connection, int amount) {
        synchronized (connection) {
            try {
                connection.open();
                return connection.withdraw(amount);
            } catch (Exception e) { ... }
            } finally {
                connection.close();
            }
        }
    }
}