The easiest programming language to learn may vary depending on individual background and experience. However, some languages commonly suggested as beginner-friendly include Python, JavaScript, Java, HTML, and CSS.

In Java, the void keyword is a reserved type used mainly to specify that a method does not return any data type. It can also be used as a non-access modifier of a constructor or method, or of a class in a class declaration. An example of its use in a method declaration is shown below:

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public void sayHello() {
    System.out.println("Hello!");
}

That depends on the type of development you'd like to pursue. JavaScript is a versatile language used in web development, making it a great language to start with. Python is a great language for data science and machine learning while Java is good for enterprise applications. Ultimately it'll come down to personal preference and goals.

For a Java alert message, you could use the following code:

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JOptionPane.showMessageDialog(null, "Your desired message");

It depends on the programming language you are using. In HTML, the body tag is the main container used to identify the main content of a webpage. In Java, a "class" is a type of object that contains related fields, methods and constructors. So, it is possible to create a class called body, though this is not a predefined class in the language.

In many programming languages, including JavaScript, Python, and Java, an array is a structured data type that stores a group of objects (items or values) of the same kind. To create an array, you must declare it first. For example, in Java, you would write the following code to declare an array of integers:

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int[] myArray = new int[4];

This declares an array with 4 elements of type int. You can assign values to each of the elements using the array's index, like this:

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myArray[0] = 40;
myArray[1] = 25;
myArray[2] = 18;
myArray[3] = 33;

It depends on the job you are considering as a cloud practitioner, but coding is often required. Cloud practitioners can use languages such as Python, Java, Ruby, and JavaScript which are commonly used to create applications or automate tasks in the cloud. They may also have to understand concepts like software architecture, data structures, and algorithms. Additionally, understanding DevOps processes and various cloud services such as containerization, databases, storage solutions, and serverless functions will be helpful.

In order to format the date time, you will need to use the appropriate date-time library in the programming language you are using. For example, in Java, you can use the java.time library to format date-time objects.

You can use the LocalDateTime.format() method to format the date-time string. By specifying a DateTimeFormatter instance, you can customize your output format.

Java example:

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import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

// Format the current date-time
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("dd-M-yyyy hh:mm:ss"); 
LocalDateTime localDateTime = LocalDateTime.now();
String dataTimeString = localDateTime.format(formatter);

System.out.println(dateTimeString);

Output: 20-8-2018 11:48:27

You can create a hovering red-blue button in CSS and Java by using the :hover pseudo-class on the <button> element. In this example, the button's color will transition from red to blue when a user's mouse pointer hovers over the button.

CSS:

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button {
    background-color: red;
}

button:hover {
    background-color: blue;
}

JavaScript:

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let button = document.querySelector('button');
button.onmouseover = function(){
  this.style.backgroundColor = 'blue';
}
button.onmouseout = function(){
  this.style.backgroundColor = 'red';
}

Java and Javascript are two very different programming languages. Java is an object-oriented, class-based, general-purpose programming language while Javascript is a prototype-based scripting language. Java is compiled into bytecode, which then runs on a virtual machine or browser, while JavaScript is an interpreted language run directly inside a web browser. Java is strongly typed, which means it requires variables to be declared before use, whereas JavaScript is a loosely typed language which allows for variables to be changed more freely.

Polymorphism is a concept in object-oriented programming (OOP) where an object can take on multiple forms. In other words, the same object can behave differently depending on the context in which it is used. For example, a Vehicle type in OOP can be a Car, a Motorcycle or a Bicycle, depending on which is being referenced. In Java, this is achieved by making a parent object (e.g. Vehicle) with common attributes and methods, and then having sub-types that inherit from the parent object and add specific attributes and methods (e.g. Car, Motorcycle and Bicycle).

In Java, Polymorphism is implemented through the use of Abstract Classes and Interfaces. Abstract Classes give the superclass the ability to define methods that all the subclasses will inherit. Interfaces on the other hand specify the type of objects that can be used by other classes, and provide a set of methods that all classes sharing the interface will have to implement.

Here is an example in Java of how polymorphism can be used:

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public abstract class Vehicle { 
  // Attributes and Methods common to all Vehicles 
} 

public class Car extends Vehicle { 
  // Unique attributes and methods applicable to only Cars 
} 

public class Motorcycle extends Vehicle { 
  // Unique attributes and methods applicable to only Motorcycles 
}

public class Bicycle extends Vehicle { 
  // Unique attributes and methods applicable to only Bicycles 
} 

The Vehicle class here defines methods and attributes that will be common to all types of vehicles, while the Car, Motorcycle and Bicycle subclasses each create specific implementations of those attributes and methods.

You can read more about Polymorphism here: https://www.geeksforgeeks.org/polymorphism-in-java/