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
Import package
To import a specific package into the current file, use import statement.
/**
* If you do not use a package statement ...
* your type (your class) goes in an unnamed package.
*
* Java compiler automaticaly imports three packages:
*
* (1) the package with no name
* (2) the java.lang package
* (3) the current package
*/
package com.minte9.oop.packages;
import java.util.ArrayList;
public class Import {
public static void main(String[] args) {
ArrayList<Integer> list = new ArrayList<>();
list.add(1);
list.add(2);
System.out.println(list); // [1, 2]
}
}
Hierarchy
At first, packages appear to be hierarchial, but they are not.
/**
* Importing java.uitl.* imports all of the types ...
* in the java.util package but it does not import ...
* java.util.regex package
*/
package com.minte9.oop.packages;
//import java.util.*; // not used
//import java.util.regex.Matcher; // Look Here
import java.util.regex.Pattern;
public class Hierarchy {
public static void main(String[] args) {
Pattern p = Pattern.compile("Java");
java.util.regex.Matcher m = p.matcher("Java SE 8");
System.out.println(m.find()); // true
}
}
➥ Questions