Java
/
Lambdas
- 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
Iterations
p27 Streams allow us to write collections code at a higher level of abstraction.
/**
* Streams allow us to write collections code ...
* at a higher level of abstraction.
*
* Iterator - external iteration
* Stream - internal interation
*/
package com.minte9.lambdas.streams;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
public class Iterations {
public static void main(String[] args) {
List<Integer> numbers = Arrays.asList(1, 2, 3);
int count = 0;
for(int n : numbers) {
if (n <= 2) count++;
}
System.out.println(count); // 2
Iterator<Integer> it = numbers.iterator();
while(it.hasNext()) {
int n = it.next();
if (n <= 2) count++;
}
System.out.println(count); // 4
long total = 0;
total = numbers.stream()
.filter(n -> n <= 2)
.count();
System.out.println(total); // 2
}
}
Lazy
Stream library was design to iterate only once (lazy evaluation).
/**
* The stream library was design to iterate only once
* (lazy evaluation)
*
* Methods that generate a final value out of the Stream sequence ...
* are called "eager"
*
* Code without an eager method doesn't print anything ...
* due to lazy evaluation
*/
package com.minte9.lambdas.streams;
import java.util.Arrays;
import java.util.List;
public class Lazy {
public static void main(String[] args) {
List<Integer> numbers = Arrays.asList(1, 2, 3);
numbers.stream().filter(n -> {
System.out.println(n);
return n <= 2;
}); // nothing
numbers.stream().filter(n -> {
System.out.println(n);
return n <= 2;
}).count(); // 1 2 3 - Look Here
}
}
➥ Questions
Last update: 28 days ago