Collection as my bag

When a person decide to travel, he keeps thinking ! !
what will i take, which bag will suits my luggage ??

Collection is our bag, container that we staff our objects in. So which ?
for an arrayList removing an element from the middle of an array is expensive "require to move up all elements beyond the removed one".
linked list saved the day, since array stores object reference in consecutive memory location, linked list stores each object in a separate link, each link stores reference to next link.
however, for linkedList.get(index) result in starting from the first till reach the index "much overhead with each look up, starts again from the beginning ". have to trade off
However, when looking for a particular element "Search: require visiting all elements till find match" use hashMap faster but have no control over the order.

Comments

The post-office & the postman

If we were to talk about old messaging system where there exist post-office, postman & mailbox. each component had its own functionality that we looked for when trying to visualize how those component where to interact in a computerized version. Simple scenario: Mail is added in mail box Postman arrive pick mails from his area mailboxes and take them to the post-office. Post-office organize mails by areas. Postman takes mails related to his area "distribute it in mailboxes". A person can go to post-office and pick his own mail "in case of failure or wishes for early delivery". Mapping in a computerized version: Scenario: Observer design pattern which can use push or pull scenario, to inform those whom are registered for an event about its occurrence. Component: Post-Office = Message-Broker Post-Office-Box = Message-Storage-Validity Mailbox = Topic/Queue Postman !!! where's the postman ? Apache kafka act as a message broker which d...

Not all Ps sting

If someone meant to say Ps and pronounce it Bees. would this confuse you :). Ps is for the P that is the start of Properties and Practice Each application should have some properties and follow certain practices. Properties: Below are 5 properties we should try to have in our application with a small description of how to include them Scalable, Scale => Increase workload (horizontally scaling) Statless, no state should be shared among different application instances, Concurrency, concurrent processing = Threads. Loosely coupled, decompose the system into modules, each has minimal dependencies on each other "modularization", encapsulating code that changes together "High cohesion". API first, Interfaces, implementation can be changed without affecting other application. favor distribution of work across different teams. Backing Services, "DB, SMTP, FTP ..." , treating them as attached resources, meaning they can easily be changed. Manageable, changi...

String literal pool

I'm used to use String .format() when constructing a SQL statement, and a friend I knew likes to concatenate saying :"it's more readable to me". So String Objects are immutable, meaning that once they are created, they can't be altered. Concatenating 2 strings doesn't modify either Strings instead, it creates a new String "old ones are added to the string pool". String literals always have a reference to them in String Literal Pool, therefore not eligible for garbage collection. to concatenate use StringBuffer (Synchronized) or StringBuilder (not Synchronized) As both uses an internal array "so that new String Objects are not created". String literal Pool : String are stored in pool and before creating a new string literals, compiler checks if such string already defined "used to optimize and save space". String literals : a sequence of characters between quotation marks.

Change

Search This Blog