Java
/
Basics
- 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
S
R
Q
Java Basics Arrays
Arrays can be created with new OR {} syntax String.join() to combine elemnents int[] A = new int[2] String[] names = {"John", "Marry", "Ana"}
Arrays
Arrays can be created with new operator, or alternatively with {} syntax.
/**
* One way to create an array is with new operator ...
* which allocates the memory for 3 elements
*
* You can also create and initialize the array with {} syntax
* Array length is the number of elements between braches
*/
package com.minte9.basics.arrays;
public class Arrays {
public static void main(String[] args) {
int[] nums;
nums = new int[2];
nums[0] = 1;
nums[1] = 2;
String[] names = {"John", "Marry", "Ana"};
System.out.println(nums[1]); // 2
System.out.println(names[2]); // Ana
try {
names[3] = "Willy";
} catch (Exception ex) {
System.out.println(ex.getMessage()); // Index 3 out of bounds
}
}
}
Types
p83 An array is forever an array.
/**
* An array is forever an array
*
* Creating an array of Dogs, not a new Dob object
*/
package com.minte9.basics.arrays;
public class Types {
public static void main(String[] args) {
Dog[] dogs = new Dog[4]; // array of Dogs
dogs[0] = new Dog();
dogs[1] = new Dog();
// dogs[2] = 222; // Compiler Error
System.out.println(dogs.length); // 4
}
}
class Dog {}
Join
Starting with Java 8 we can use String.join() method.
/**
* Array string elements can be joined with ...
* String.join() method (since JDK 1.8)
*/
package com.minte9.basics.arrays;
public class Join {
public static void main(String[] args) {
String[] A = new String[] {"a", "b", "c"};
System.out.println(
String.join(", ", A) // a, b, c
);
}
}
➥ Questions