Java
/
OOP
- 1 Basics 9
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Classes S
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Objects S
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Arrays S
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Variables S
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Loops S
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Numbers S
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Strings S
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Exceptions S
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Regexp S
- 2 OOP 9
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Inheritance
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Polymorphism
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Static S
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Abstract
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Interfaces
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Constructors S
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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 S
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Apache Ant
- 4 Collections 8
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Lists
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Comparable S
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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 S
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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 S
- 9 Effective 7
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Constructors S
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Dependency Injection
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Composition
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Interfaces Default
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Import Static S
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Enums
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Lambdas
- 10 Junit 5
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About Junit S
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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 S
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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 S
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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 13
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Quick start S
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Rest service S
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Consuming rest S
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Templates S
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Security auth S
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Command line S
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Scheduled task S
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Ajax S
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Jdbc mysql S
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Encrypt password S
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Https S
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Jwt S
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Post request S
R
Q
Inheritance
p181 Don't use inheritance just to reuse code.
/**
* Inheritance means that a subclass extends a super class.
* Superclasses defines what subclasses have in common ...
* then abstract those features.
*
* Every class in Java extends class Object.
* Object is the only class that has no superclass.
*/
package com.minte9.oop.inheritance;
public class Inheritance {
public static void main(String[] args) {
Dog dog = new Dog();
dog.setAction("barking");
dog.action(); // The Dog is barking
Bird bird = new Bird();
bird.setAction("flying");
bird.action(); // The Bird is flying
}
}
abstract class Animal {
public String action;
public void setAction(String a) {
action = a;
}
public abstract void action();
}
class Dog extends Animal {
@Override public void action() {
System.out.println(
"The Dog is " + action
);
}
}
class Bird extends Animal {
@Override public void action() {
System.out.println(
"The Bird is " + action
);
}
}
Annotation
Override annotation acts as a compile-time safeguard.
/**
* Abstract method with no Override annotation ...
* will throw error only at compile time.
*/
package com.minte9.oop.inheritance;
public class Annotation {
public static void main(String[] args) {
new MyClass();
}
}
abstract class MyAbstractClass {
abstract public void setName();
}
class MyClass extends MyAbstractClass {
// Wrong method name - with no Override annotation)
public void setNames() {}
// Correct - with Override annotation
@Override
public void setName() {}
}
Super
p254 The super() method is used to call parent constructor.
/**
* super() method is used to call parent constructor
* It must be the first statement in each controller
*/
package com.minte9.oop.inheritance;
public class Super {
public static void main(String[] args) {
new A();
}
}
class A extends ParentClass {
public A() {
super(); // Parent constructor
}
/*
public void A(String s) {
// Wrong, void is the first statement
super(s);
}
*/
}
class ParentClass {
public ParentClass() {
System.out.println("Parent constructor");
}
}
➥ Questions