Coding Compiler Reference datatypes in java are those which contains reference/address of dynamically created objects. These are not predefined like primitive data types. Different Reference Types java.lang.ref package provides reference-object classes, which support a limited degree of interaction with the garbage collector. Java has four main different reference types. They are: Strong Reference Weak Reference Soft Reference Phantom … Read more
The idea behind programming to an interface is to base the code primarily on interfaces and only use concrete classes at the time of instantiation. In this context, good code dealing with e.g. Java collections will look somethinglike this (not that the method itself is of any use at all, just illustration): public Set toSet(Collection … Read more
The Liskov Substitution Principle, which provides a lot of details on it. As per the LSP, functions that use references to base classes must be able to use objects of the derived class without knowing it. In simple words, derived classes must be substitutable for the base class. To illustrate the LSP, let’s take an … Read more
package in java is used to group class and interfaces. This helps developer to avoid conflict when there are huge numbers of classes. If we use this package the classes we can create a class/interface with same name in different packages. By using packages we can import the piece of again in another class. There … Read more
Default Method introduced in Java 8, allows developers to add new methods to an interface without breaking the existing implementations of this interface. It provides flexibility to allow the interface to define an implementation which will be used as default when a class which implements that interface fails to provide an implementation ofthat method. Basic … Read more
Local Inner Classes are the inner classes that are defined inside a block. Generally, this block is a method body. … These classes have access to the fields of the class enclosing it. Local inner classes are must be instantiated in the block they are defined in. Basic Object Construction and Use in Java Objects come Basic Object Construction and Use in Java in … Read more
There are many differences between method overloading and method overriding in java. A list of differences between method overloading and method overriding are given below: Objects have states and behaviors. Example: A dog has states – color, name, breed as well as behaviors – wagging the tail, barking, eating. An object is an instance of … Read more
Generics are a facility of generic programming that extend Java’s type system to allow a type or method to operate on objects of various types while providing compile-time type safety. In particular, the Java collections framework supports generics to specify the type of objects stored in a collection instance. Related Article: Visibility (controlling access to … Read more
Private Visibility private visibility allows a variable to only be accessed by its class. They are often used in conjunction with public getters and setters. class SomeClass { private int variable; public int getVariable() { return variable; } public void setVariable(int variable) { this.variable = variable; } } public class SomeOtherClass { public static void … Read more
An object is considered immutable if its state cannot change after it is constructed. Maximum reliance on immutable objects is widely accepted as a sound strategy for creating simple, reliable code Creating an immutable version of a type using defensive copying Some basic types and classes in Java are fundamentally mutable. For example, all array types are mutable, and so are … Read more
Immutable objects are instances whose state doesn’t change after it has been initialized. For example, String is an immutable class, and once instantiated its value never changes. Example without mutable refs public final class Color { final private int red; final private int green; final private int blue; private void check(int red, int green, int … Read more
This article is an intro to Java source-level annotation processor and provides examples of using this technique for generating additional source files during compilation. This example demonstrates how to do compile time checking of an annotated element. The annotation The @Setter annotation is a marker can be applied to methods. The annotation will be discarded during compilation … Read more
In Java, an annotation is a form of syntactic metadata that can be added to Java source code. It provides data about a program that is not part of the program itself. Annotations have no direct effect on the operation of the code they annotate. Classes, methods, variables, parameters and packages are allowed to be … Read more
The Java language provides three operator for performing bitwise shifting on 32 and 64 bit integer values. These are all binary operators with the first operand being the value to be shifted, and the second operand saying how far to shift. The << or left shift operator shifts the value given by the first operand … Read more
This documentation page is for showing details with example about java class constructors and about Object Class Methods which are automatically inherited from the superclass Object of any newly created class. hashCode() method When a Java class overrides the equals method, it should override the hashCode method as well. As defined in the method’s contract: … Read more
While not required, constructors in Java are methods recognized by the compiler to instantiate specific values for the class which may be essential to the role of the object. This topic demonstrates proper usage of Java class constructors. Default Constructor The “default” for constructors is that they do not have any arguments. In case you … Read more
The cybersecurity industry is worth over 100 billion dollars, and as more and more companies are opting to adopt cloud services, IoT, and complex networks, the sum is skyrocketing each year. Consequently, the number of people willing to venture into this IT sector is rising as well. And many of those choose the Exam-Labs Practice … Read more
Operators in Java programming language are special symbols that perform specific operations on one, two, or three operands, and then return a result. The Increment/Decrement Operators (++/–) Variables can be incremented or decremented by 1 using the ++ and — operators, respectively. When the ++ and — operators follow variables, they are called post-increment and … Read more
Maps provide methods which let you access the keys, values, or key-value pairs of the map as collections. Iterating through the contents of a Map. You can iterate through these collections. Given the following map for example: Map repMap = new HashMap<>();repMap.put(“Jon Skeet”, 927_654);repMap.put(“BalusC”, 708_826);repMap.put(“Darin Dimitrov”, 715_567); Iterating through map keys: for (String key : … Read more
The java.util.Map interface represents a mapping between keys and their values. A maps cannot contain duplicate keys; and each key can maps to at most one value. Since Maps is an interface, then you need to instantiate a concrete implementation of that interface in order to use it; there are several Maps implementations, and mostly … Read more