Java
/
OOP
- 1 Basics 9
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Classes
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Objects
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Arrays
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Variables
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Loops
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Numbers
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Strings
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Exceptions
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Regexp
- 2 OOP 9
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Inheritance
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Polymorphism
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Static
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Abstract
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Interfaces
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Constructors
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Packages
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Nested Classes
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Final
- 3 Compiler 2
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Sublime Text
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Apache Ant
- 4 Collections 8
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Lists
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Comparable
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Sets
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Maps
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Generics
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Properties
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Streams
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Json
- 5 Threads 4
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Create Thread
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Sleep
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Lock
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Scheduler
- 6 Design patterns 4
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Singleton
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Observer
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Strategy
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Mediator
- 7 Swing 12
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Frame
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Panel
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Listener
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Combo Box
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Label
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Image
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Menu
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Table
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Layout
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Drawing
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Timer
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Designer
- 8 I/O 7
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Streams IO
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Socket
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Watching Files
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Mail
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Logger
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Clipboard
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Encrypt
- 9 Effective 7
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Constructors
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Dependency Injection
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Composition
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Interfaces Default
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Import Static
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Enums
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Lambdas
- 10 Junit 5
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About Junit
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Test Case
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Suite Test
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Annotations
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Exceptions
- 11 Lambdas 7
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Expressions
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Functional Interfaces
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Streams
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Common Operations
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Default Methods
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Static Methods
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Single Responsibility
- 12 JavaFX 6
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Openjfx
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Scene Builder
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First App
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Jar Archive
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On Action
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Change Listener
- 13 Maven 4
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Demo
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Spring Boot
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Junit
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Guava
- 14 Spring Boot 8
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Quick start
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Rest service
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Consuming Rest
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Templates
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Security
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Command Line
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Scheduling Tasks
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Ajax
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Abstract Keyword
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Last update: 17-06-2022
Classes
p 201 Abstract classes can't be instantiated.
/**
* By marking the class abstract, you can prevent instantiation.
*
* What exactly is an Animal object, what color, what size?
* We don't know, so the class must be defined as abstract.
*/
package com.minte9.oop.abstract_keyword;
public class Classes {
public static void main(String[] args) {
new Dog("gray");
//new Animal(); // force compile error - what color?
}
}
abstract class Animal {
protected String color;
public Animal(String c) {
color = c;
}
}
class Dog extends Animal {
public Dog(String c) {
super(c);
}
}
Methods
p 203 An abstract method must be overridden.
/**
* An abstract class means ... the class must be extended.
* An abstract method means ... the method must be overridden.
*/
package com.minte9.oop.abstract_keyword;
public class Methods {
public static void main(String[] args) {
new D();
}
}
abstract class A {
public abstract void setValue(); // abstract
public void setName() { // non-abstract
}
}
class D extends A {
@Override
public void setValue() { // Look Here
}
}
➥ Questions github OOP