#anonymous inner class

[facingissuesonit]

Java 8: Lambda Expression

Java 8: Lambda Expression

Java 8 introduced lambda expression to move toward functional programming. A lambda expression is an anonymous function that doesn’t have a name and doesn’t belong to any class.

Where to use the Lambda Expression

A lambda expression can only be used where the type they are matched against is a single abstract method(SAM) interface or functional interface.

To use a lambda expression, you can…

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[itsbeyondsimple-blog]

5 Uses of Boxing and AutoBoxing in JavaTitle

Sine the development and introduction of JDK version 5, Java has provided different features like autoboxing, unboxing, and boxing. All these features generally mean conversion bet

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[itsbeyondsimple-blog]

Want to Understand the Implementation of Java Map Interface? Read Here!

Java Map Interface is about the process of mapping between a key and a value. One must understand that Java Map Interface is not a subtype of the Collection interface. Hence, it acts distinctly in …

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[itsbeyondsimple-blog]

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[johnchen]

Java - Anonymous Inner Classes

In an earlier post, I said that you could not use new on abstract classes and interfaces since they were just blueprints of a class and not complete. They provide signatures for the methods, but no implementation, so of course new wouldn’t work.

However, you CAN use new on abstract classes and interfaces, but it basically requires you to provide the implementation on the spot.

This is how it works:

Repl.it: https://repl.it/repls/UnwillingGentleOs

Let’s say you have an interface:

interface Pet {  public void greet(); }

I can call new on it by doing the following:

class Main {  public static void main(String[] args) {    Pet dog = new Pet() {      @Override      public void greet() {        System.out.println("Woof!");      }    };

   dog.greet();  } }

Basically, I am writing a class that implements Pet on the spot and making a new instance of that, which I am calling dog.

Why is this useful?

- This allows you to skip creating a whole class in a different file if you are absolutely sure you are only going to use that particular class only once.

- Lambda expressions are only available in Java 8 and up so this is how you would do it if you did not have the ability to use Java 8 features.

Java 7

Collections.sort(listOfCars, new Comparator<Car>(){

  public int compare(Car c1,Car c2){

    // Write your logic here.

}});

Java 8

Collections.sort(listOfCars, (c1, c2) -> {

  // Write your logic here

}));

[javacjava-blog]

Learn Java Programming - Anonymous Inner Class Implementing an Interface Tutorial

An anonymous inner class is a nested class defined without any name. An anonymous class is entirely dependent upon either a superclass or interface in order to work properly. This tutorial will focus on the version that is dependent upon an interface. You may also want to brush up on your Runnable skills by watching my Creating a Thread Part Three Tutorial. Also I highly recommend understanding all the concepts in my Anonymous Inner Class Extending a Superclass Tutorial as well.

[zishanbilal-blog-blog]

Ever since is heard Java 8 going to support lambda expressions (aka closures), I was very enthusiastic to spice my code with such a decent and concise functional element. Most developers extensively use Anonymous Inner Classes for event handlers, comparators, basic thread/runnable implementations, etc and overburden the logic with unnecessary scaffoldings even a very simple piece of code seems complex and unwieldy. Java 8 now added Lambda expressions as part of language syntax that help solve similar problem in a very elegant manner. It enable developers to encapsulate a single unit of behavior and pass it to other code. It’s like syntactic sugar for an anonymous class (with one method whose type is inferred) and is an object-less method. I prefer avoiding extensive theoretical material in this post, but before moving further towards understanding the syntax, structure and examples of lambdas, there is an important concept need attention.

[chippertohacker]

[Android] Anonymous Inner classes

Something that is used very often in Android programming, are the Java constructs, anonymous inner classes. They are used to create things like onClickListeners and start new intents.

Inner classes are basically classes that are embedded within another class. Just like top-level classes, inner classes can have methods and their own variables. 

A couple of tricky things about these inner classes:

- They can only call member variables of the outer class directly if those instance variables are of type "final" i.e., the instance variables are immutable. This is because the instance variables and the inner classes will likely be compiled at different times. The outer class instance variable may be complied at run time, but the inner class may only be called once used

- If you want to call an outer-class non-final instance variable from an inner class, you can use the convention:

OuterClassName.this.instanceVariableName