Java Flashcards

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Java is a versatile, object-oriented programming language created by James Gosling at Sun Microsystems. It is a language designed with portability and security in mind, allowing for the creation of applications that run on various platforms without the need for recompilation. Java is characterized by strong typing and an extensive library ecosystem, allowing for the efficient creation of both desktop applications and complex enterprise systems. This language offers advanced memory management and multithreading mechanisms, providing developers with tools for building scalable and efficient applications while maintaining high reliability and ease of code maintenance.

Our flashcard app includes carefully selected Java interview questions with comprehensive answers that will effectively prepare you for any interview requiring Java knowledge. IT Flashcards is not just a tool for job seekers - it's a great way to reinforce and test your knowledge, regardless of your current career plans. Regular use of the app will help you stay up-to-date with the latest Java trends and keep your skills at a high level.

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What is Java and on which platforms can it be run?

Java is a programming language created by Sun Microsystems (now owned by Oracle Corporation) that is object-oriented, class-oriented, strongly typed, compiled to bytecode, and then interpreted by the Java Virtual Machine (JVM).

Java is renowned for its high level of portability between different operating systems - the code is always compiled to bytecode, which can be interpreted on any platform that has a Java Virtual Machine installed. This means that the same program written in Java can be run on many different operating systems, such as Windows, Linux, MacOS, without any additional modification.

The Java Virtual Machine (JVM) is the foundation of Java technology. It is a software platform that operates in conjunction with the operating system and provides an environment for running Java code.

This only briefly describes Java technology. Its features such as multi-threading support, automatic memory management, security with sandbox, support for networks and communication between applications, and the multitude of available libraries and frameworks, make Java one of the most popular programming languages in the world.

What are the basic data types in Java?

Java offers the following basic data types:

1. Number Types:
* byte: An 8-bit integer type ranging from -128 to 127.
* short: A 16-bit integer type. Range from -32768 to 32767.
* int: A 32-bit integer type. Range from -2147483648 to 2147483647. It is the most commonly used integer type.
* long: A 64-bit integer type. Range from -9223372036854775808 to 9223372036854775807.
* float: A 32-bit floating-point type. It can store up to 6 - 7 digits after the decimal point.
* double: A 64-bit floating-point type. It can store up to 15 digits after the decimal point. It is the most commonly used type for floating point numbers.

2. Character Type:
* char: A 16-bit character type used for storing unicode characters.

3. Logical Type:
* boolean: Type used for storing a logical value (true/false).

These are the basic primitive data types, but Java also offers reference types, which are the wrapper version of the primitive types, such as Integer, Double, Boolean etc.

How do you create a variable in Java?

Creating a variable in Java involves declaring its type, giving it a name, and optionally assigning it a value. The variable's type can be any data type, such as int (integer), double, String and so on.

The main syntax for declaring a variable is as follows:

type variable;

Where "type" is the data type and "variable" is the variable's name.

If you want to declare a variable and simultaneously assign a value to it, you use the syntax:

type variable = value;

Example:

int number;
String name;
double survey;

number = 10; // Assign a value to the variable
name = "Java"; // Assign a value to the variable
survey = 9.75; // Assign a value to the variable

You can also declare multiple variables of the same type in one line, separating them with commas, for example:

int a = 2, b = 4, c = 6;

What is a loop in programming and what loops are available in Java?

A loop in programming is a control structure that repeats a block of code a certain number of times or until a certain condition is met. Loops are extremely useful in programming, as they allow the same operations to be performed on multiple elements, without having to write the same code multiple times.

In Java, the following types of loops are available:

1. For loop: Most commonly used for iteration over a sequence. It typically consists of three elements: initialization (where we set the initial value of our control variable), condition (whose fulfillment allows for the execution of subsequent iterations) and incrementation (where we modify the value of the control variable).

for(int i = 0; i < 10; i++) {
    System.out.println(i);
}

2. While loop: Executes a block of instructions as long as the condition is true.

int i = 0;
while(i < 10) {
    System.out.println(i);
    i++;
}

3. Do-while loop: This is similar to the while loop, but with the difference that the condition is checked at the end of each iteration - meaning that the block of instructions will be executed at least once.

int i = 0;
do {
    System.out.println(i);
    i++;
} while(i < 10);

4. For-each loop: This is a specific type of for loop, adapted for iteration over collections and arrays.

int[] numbers = {1,2,3,4,5};
for(int number : numbers) {
    System.out.println(number);
}