Fundamentals of Java Programming Language

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Java is an object-oriented programming language that has become one of the most popular languages in the world. It’s a high-level, versatile language used for developing large-scale applications, including Android apps, web applications, and enterprise software.

What is Java?

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History of Java

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Java was created by James Gosling and his team at Sun Microsystems (now owned by Oracle) in the mid-1990s. The first version of Java, known as Oak, was developed in 1991, but it wasn’t until the release of Java 1.0 in 1995 that the language gained popularity.

Key Features

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Java’s key features make it an attractive choice for developers:

• Platform independence: Java code can run on any platform that has a Java Virtual Machine (JVM) installed.
• Object-oriented: Java supports encapsulation, inheritance, and polymorphism, making it easier to write reusable code.
• Simple syntax: Java’s syntax is easy to learn and use, especially for beginners.

Basic Syntax

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Variables and Data Types

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Java has eight primitive data types:

Data Type	Description
byte	8-bit signed integer
short	16-bit signed integer
int	32-bit signed integer
long	64-bit signed integer
float	32-bit floating-point number
double	64-bit floating-point number
boolean	true or false value
char	single character

int x = 10; // Declare and initialize an integer variable

Operators

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Java has various operators for performing arithmetic, comparison, logical, and assignment operations:

• Arithmetic operators: +, -, *, /, %
• Comparison operators: ==, !=, >, <, >= , <=
• Logical operators: && (and), || (or)
• Assignment operator: =

int x = 5;
int y = 10;

System.out.println(x + y); // Output: 15

Control Structures

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Java’s control structures are used to control the flow of a program:

• Conditional statements:
• If-else statements (if, else)
• Switch statements (switch)
• Loops:
• For loops (for)
• While loops (while)

int x = 10;
if (x > 5) {
System.out.println("x is greater than 5");
} else {
System.out.println("x is less than or equal to 5");
}

Classes and Objects

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Classes

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A class in Java is a blueprint for creating objects. It defines the properties and behavior of an object:

public class Person {
private String name;
private int age;

public void setName(String name) {
this.name = name;
}

public void setAge(int age) {
this.age = age;
}

public String getName() {
return name;
}

public int getAge() {
return age;
}
}

Objects

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An object in Java is an instance of a class. It has its own set of attributes (data) and methods (functions):

public class Main {
public static void main(String[] args) {
Person person = new Person();
person.setName("John");
person.setAge(30);

System.out.println(person.getName()); // Output: John
System.out.println(person.getAge());  // Output: 30
}
}

Inheritance and Polymorphism

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Inheritance

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Inheritance in Java allows one class to inherit properties and behavior from another class:

public class Animal {
private String name;

public void setName(String name) {
this.name = name;
}

public String getName() {
return name;
}
}

public class Dog extends Animal {
private int age;

public void setAge(int age) {
this.age = age;
}

public int getAge() {
return age;
}
}

Polymorphism

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Polymorphism in Java allows objects of different classes to be treated as if they were of the same class:

public class Main {
public static void main(String[] args) {
Animal animal = new Dog();
animal.setName("Max");
((Dog)animal).setAge(2);

System.out.println(animal.getName()); // Output: Max
System.out.println(((Dog)animal).getAge());  // Output: 2
}
}

This concludes the basics of Java programming language. With this knowledge, you can start building your own Java programs and explore more advanced concepts in object-oriented programming.

Additional Resources

For further learning, check out the official Java documentation and online resources like Codecademy’s Java course or Udemy’s Java courses.