Java
/
OOP
- 1 Basics 9
-
Classes S
-
Objects S
-
Arrays S
-
Variables S
-
Loops S
-
Numbers S
-
Strings S
-
Exceptions S
-
Regexp S
- 2 OOP 9
-
Inheritance
-
Polymorphism
-
Static S
-
Abstract
-
Interfaces
-
Constructors S
-
Packages
-
Nested Classes
-
Final
- 3 Compiler 2
-
Sublime Text S
-
Apache Ant
- 4 Collections 8
-
Lists
-
Comparable S
-
Sets
-
Maps
-
Generics
-
Properties
-
Streams
-
Json
- 5 Threads 4
-
Create Thread S
-
Sleep
-
Lock
-
Scheduler
- 6 Design Patterns 4
-
Singleton
-
Observer
-
Strategy
-
Mediator
- 7 Swing 12
-
Frame
-
Panel
-
Listener
-
Combo Box
-
Label
-
Image
-
Menu
-
Table
-
Layout
-
Drawing
-
Timer
-
Designer
- 8 I/O 7
-
Streams IO
-
Socket
-
Watching Files
-
Mail
-
Logger
-
Clipboard
-
Encrypt S
- 9 Effective 7
-
Constructors S
-
Dependency Injection
-
Composition
-
Interfaces Default
-
Import Static S
-
Enums
-
Lambdas
- 10 Junit 5
-
About Junit S
-
Test Case
-
Suite Test
-
Annotations
-
Exceptions
- 11 Lambdas 7
-
Expressions S
-
Functional Interfaces
-
Streams
-
Common Operations
-
Default Methods
-
Static Methods S
-
Single Responsibility
- 12 JavaFX 6
-
Openjfx
-
Scene Builder
-
First App
-
Jar Archive
-
On Action
-
Change Listener
- 13 Maven 4
-
Demo
-
Spring Boot
-
Junit
-
Guava
- 14 Spring Boot 13
-
Quick start S
-
Rest service S
-
Consuming rest S
-
Templates S
-
Security auth S
-
Command line S
-
Scheduled task S
-
Ajax S
-
Jdbc mysql S
-
Encrypt password S
-
Https S
-
Jwt S
-
Post request S
R
Q
Final
Final classes / methods cannot be extended / overriden.
/**
* A final class cannot be exended.
* A final method cannot be overriden.
*/
package com.minte9.oop.final_keyword;
public class Final {
public static void main(String[] args) {
new B();
}
}
class A {
public final void getName() { // Look Here
}
}
final class B extends A {
/*
public void getName() {
// Error: override final method
}
*/
}
/*
class C extends B {
// C cannot subtype finalclass B
}
*/
Constants
Fields that are static and final are constants (it can never change).
/**
* A static final variables is a constant.
* It cannot be changed.
*/
package com.minte9.oop.final_keyword;
public class Constants {
public static void main(String[] args) {
new MyClass(); // 25
}
}
class MyClass {
public static final int FOO = 25; // Look Here
public MyClass() {
System.out.println(FOO);
// FOO++; // Compile Error - Look Here
}
}
➥ Questions
Last update: 516 days ago