This article is the extension of Observer Pattern. In this we will try to relate this pattern with Android framework so that it would be easy for Android enthusiasts to relate better. If you are seeking for some more deep basic understanding on Observer Pattern, you can ……………
The Observer Pattern is a software design pattern that establishes a one-to-many dependency between objects. Anytime the state of one of the objects (the “subject” or “observable”) changes, all of the other objects (“observers”) that depend on it are notified. Before starting this Observer Design Pattern, I would ……………
In Java the Singleton pattern will ensure that there is only one instance of a class is created in the Java Virtual Machine. It is used to provide global point of access to the object. In terms of practical use Singleton patterns are used in logging, caches, ……………
Design patterns are typical solutions to commonly occurring problems in software design. They are like pre-made blueprints that you can customise to solve a recurring design problem in your code. You can’t just find a pattern and copy it into your program, the way you can with ……………
How can we prove that Java and Kotlin can co-exist and its interoperable? Kotlin is designed with Java Interoperability in mind. Existing Java code can be called from Kotlin in a natural way, and Kotlin code can be used from Java rather smoothly as well. In this section ……………
Writing our Hello World project in Android studio 3.0.0 using Kotlin and Java.
Let’s start this activity with one example. You can pick any example in this case. Here I just want to showcase that all the existing Android Java files(entire application) can be converted to Kotlin syntax. So I am going to consider one of my existing Android Java ……………
If you have some doubt then I recommend you to have a look on above video for more better understanding. You can put your question also in the comment section below.
This tutorial will cover how to fetch JSON from assets folder and parse it. We will use GSON, a JSON parsing library developed by Google, to quickly parse the JSON into Java objects with very minimal work required.
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dependencies { compile 'com.google.code.gson:gson:2.8.0' // Latest as of April 2017 } |
Error Log
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<strong>Error</strong>:java.lang.OutOfMemoryError: GC overhead limit exceeded Or <strong>Error</strong>:Execution failed for task ':projectName:transformClassesWithDexForDebug'. > com.android.build.api.transform.TransformException: com.android.ide.common.process.ProcessException: java.util.concurrent.ExecutionException: com.android.ide.common.process.ProcessException: org.gradle.process.internal.ExecException: Process 'command '/Library/Java/JavaVirtualMachines /jdk1.8.0_101.jdk/Contents/Home/bin/java'' finished with non-zero exit value 3 |
In my this tutorial, I am going to demonstrate how to extract method details with Annotation details with Reflection mechanism. Have a look on complete details and let me know if I you need some more details. Below interface is @Retention.RUNTIME Annotation enabled.
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package www.technicaljungle.com; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; @Retention(RetentionPolicy.RUNTIME) public @interface RefRetentionInterface { String value(); } |
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Meta data is some kind of description that you can supply along with your data. In java it’s possible to do with annotations, XML, there are other methods. In order to take advantage of meta data you should have something that will process this data and decide ……………
This is a bit of a complex annotation type. It indicates that the annotated class with this type is automatically inherited. More specifically, if you define an annotation with the @Inherited tag, then annotate a class with your annotation, and finally extend the class in a subclass, ……………
The ‘@documented’ annotation indicates that an annotation with this type should be documented by the javadoc tool. By default, annotations are not included in javadoc. But if @Documented is used, it then will be processed by javadoc-like tools and the annotation type information will also be included ……………
The retention annotation indicates where and how long annotations with this type are to be retained. There are three values: SOURCE—Annotations with this type will be by retained only at the source level and will be ignored by the compiler. CLASS—Annotations with this type will be by ……………
Meta Annotation which is also called as Annotation of Annotation. This is of four types: Target Retention Documented Inherited The Target Annotation The target annotation indicates the targeted elements of a class in which the annotation type will be applicable. It contains the following enumerated types as ……………
There are two types of annotations available with JDK5: Simple annotations: These are the basic types supplied with Tiger, which you can use to annotate your code only; you cannot use those to create a custom annotation type. Meta annotations: These are the annotation types designed for annotating annotation-type ……………
Rules of Thumb for Defining Java Annotation Types Here are some rules-of-thumb when defining an annotation type: Annotation declaration should start with an ‘at’ sign like @, following with an interface keyword, following with the annotation name. Method declarations should not have any parameters. Method declarations should ……………
Introduction Annotation is code about the code, that is metadata about the program itself. In other words, organized data about the code, embedded within the code itself. It can be parsed by the compiler, annotation processing tools and can also be made available at run-time too. First ……………
Exception handling works by transferring the execution of the program to an appropriate exception handler. For example, if you try to open a file to do some operation then situation aises like, File doesnot exist Some network problem No permission to open or read or write the ……………
Exception Exception (or an exceptional event) which occurs when the program is in execution which can change the normal flow of the program. An Exception is the instance of java.lang. Exception is further classified into two parts: Checked Unchecked Checked Exception It will be checked at compile ……………
The ability to define behaviour that’s specific to a particular subclass type. It means a method is implemented in superclass and subclass has some specific behaviour so subclass is free to implement the same method again. This concept is called as overriding. Important Points Inheritance is required to achieve Overriding. Overriding is runtime polymorphism. ……………
Overloaded methods allows to reuse the same method name in a class, but having different signature. Signature means one method varies with other method in terms of below points: Number of arguments. Types of arguments. Order of arguments. There are some rules as below: Overloaded methods must ……………
Abstract class is the class which can hold fully implemented methods and unimplemented methods. That’s the major difference between Interface vs Abstract class. Have a look on below section 1.0, which demonstrate template for Abstract class.
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Section 1.0 package technical.jungle.com.abstractdemo; public abstract class TechnicalJungleAbstract { void showValue(){ System.out.println("www.technicaljungle.com \t Value = " + someComplexCalculation()); } private int someComplexCalculation(){ /*This method is hidden from classes, who all are going to inherit this abstract class.*/ return (int) (Math.random()*10) * setValue(); } public abstract int setValue(); } Section 1.1 package technical.jungle.com.abstractdemo; public class JungleFirst extends TechnicalJungleAbstract{ public static void main(String[] args) { JungleFirst first = new JungleFirst(); first.showValue(); } @Override public int setValue() { return 1; } } Output : www.technicaljungle.com Value = 5 ( this value will be random) |
Some key points about above demo: abstract keyword is used. ……………
Interface and its usage Interface is a 100% abstract class. It means its method should not have its body part. Signatures below: User version
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interface InterfaceDemo { int onSuccess(); int onFail(); } |
Some key points for above demo: 1) Keyword “interface” used here for declaring it. 2) No method body. No curly braces like {…}. ……………
Interface Click here for complete interface explanation. Can have only unimplemented methods. Supports multiple inheritance Can have only static and final variables. Methods can’t be static. Interface can’t hold main method or constructor. Interface can’t extend/implement abstract class. Keyword ‘interface’ is used to declare. Interface can extend other ……………