[JAVA] Terms that inexperienced engineers want to remember

Overview

I have been studying various technologies for about half a year since I jumped into the IT industry. However, I did this, but there are many things that I wondered, so I will write the basics as a memorandum.

JAVA

·override → Overwrite the method defined in the superclass with the subclass ·Overload → Define a method with the same name but different arguments and return values ・ Polymorphism → Mechanism that behavior differs depending on the object to be handled even with the same operation ・ Inheritance → Define a new class based on a certain class ·object → Define multiple classes and use the objects created from the classes. [Characteristics] Highly reusable and resistant to specification changes ・ Abstract class → Class that defines one or more abstract methods [Characteristics] You can specify abstract, define methods, cannot instantiate, and have no implementation. ·Encapsulation → Set access modifiers such as public and private appropriately to restrict access to the class. [Characteristics] Since class access is unified, independence is enhanced, bugs can be prevented, and class changes are easy. ・ Difference between ArrayList and LinkedList → ArrayList is strong for access, LinkedList is strong for addition and deletion 【Reason】 (1) ArrayList implements the List interface and can be easily searched because it has the element number of the array. (2) LinkedList is the link information that the elements have before and after, and they are connected in a beaded state, so it is easy to add information. Around DB

-Difference between SQL inner join and outer join → inser join brings the ones that have the same conditions and have values in the table, but outer join can get even if the values are in only one table. ·index → Indexing speeds up data reference ·sequence → Used when creating a column that identifies data in the first place (when you do not want to duplicate ID, student number, etc.) WEB application vulnerabilities

· Application buffer overflow → Send a large number of files and cause the system to go down ・ XSS → A malicious script is executed when a user accesses a web page. As a result, unauthorized login is executed. ・ CSRF Cross-site forgery → The process that the web application user did not intend is executed. Execution of processing on an unintended WEB application. Various other things

·Batch processing → Register a series of procedures to execute work consisting of multiple programs in a batch and continuously. Aggregation processing or batch processing! ・ Deploy → To be able to use applications and systems under specific environments.

Finally

I tried to summarize the early parts. I understand the words, but there were a few terms that I thought would not be possible if they were explained. I hope it can be implemented with a basis!