Java
/
Collections
- 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
-
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
Size
p132 ArrayList don't need a size.
/**
* ArrayList class is a resizable array,
* ArrayList don't need an index and are parameterized.
*/
package com.minte9.collections.lists;
import java.util.ArrayList;
public class Size {
public static void main(String[] args) {
String[] myList = new String[2]; // Corect, with dimension
System.out.println(myList.length); // 2
// myList = new String[]; // Error: must provide dimension
ArrayList<String> myArrayList;
myArrayList = new ArrayList<>(); // no dimension needed
System.out.println(myArrayList.size()); // 0
myArrayList.add("a");
System.out.println(myArrayList.size()); // 1
System.out.println(myArrayList.contains("a")); // true
ArrayList<Button> myButtons = new ArrayList<>(); // parameterized
myButtons.add(new Button());
System.out.println(myButtons.size()); // 1
}
}
class Button {
}
Loop
You can loop through an ArrayList with the enhanced for.
/**
* ArrayList can be parsed easily with enhanced for.
*
* ArrayDeque can add elements to the head as fast as to the tail.
* If you are modifing the tail only, the ArrayList is a preferred.
*/
package com.minte9.collections.lists;
import java.util.ArrayDeque;
import java.util.ArrayList;
public class Loop {
public static void main(String[] args) {
ArrayList<String> myList = new ArrayList<String>();
myList.add("a");
myList.add("b");
myList.add(0, "c"); // add to first position
for(String v:myList) {
System.out.println(v); // c a b
}
ArrayDeque<Integer> myDeque = new ArrayDeque<>();
myDeque.addFirst(1);
myDeque.add(2);
myDeque.addLast(10);
myDeque.forEach(System.out::println); // 1 2 10
}
}
➥ Questions