java tutorialspoint with code examples

Java is one of the most popular programming languages today. It is a versatile language that allows developers to create a variety of applications ranging from small mobile applications to large enterprise systems. Since Java programs are platform-independent, they can run on any machine with a Java Virtual Machine (JVM) installed. This makes it easy for developers to write once and run anywhere.

In this tutorial, we’ll cover the basics of Java programming and provide some code examples to help you get started.

Installing Java

Before you can begin programming in Java, you must first install the Java Development Kit (JDK) on your computer. The JDK includes the Java Runtime Environment (JRE) which is required to run Java programs. The JRE includes the Java Virtual Machine (JVM), necessary libraries, and other components that support the execution of Java applications.

Once you have installed the JDK, you can check if it is installed correctly by opening the command prompt or terminal and typing “java -version”. This command will display the version of Java currently installed on your computer.

Creating your first Java program

Now that you have installed the JDK, you can begin coding your first Java program. Create a file called “HelloWorld.java” in any text editor and paste the following code into it:

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello World!");
    }
}

This is a simple Java program that prints “Hello World!” to the console. Let’s break down what each line of code does.

On the first line, we declare a public class called “HelloWorld” which contains the main method that is required for every Java program. Inside the main method, we use the System.out.println() method to print the string “Hello World!” to the console. Finally, we close the main method and the class definition.

To compile this program, navigate to the directory where your “HelloWorld.java” file is located using the command prompt or terminal. Then type “javac HelloWorld.java” to compile the program. This will create a new file called “HelloWorld.class” in the same directory.

To run the compiled program, type “java HelloWorld” in the command prompt or terminal. This will execute the program and print “Hello World!” to the console. Congratulations, you’ve just written your first Java program!

Variables and Data Types

In Java, variables are used to store data that can be used throughout the program. There are different types of data that can be stored in a variable, depending on the kind of data you want to store. Here are some of the common data types in Java:

int – used to store whole numbers (e.g. 1, 2, -3)
double – used to store floating-point numbers (e.g. 3.14, 2.718)
boolean – used to store true or false values
String – used to store a sequence of characters (e.g. “Hello”, “World”)

Here is an example of how to declare and initialize variables in Java:

int num = 10;
double pi = 3.14159;
boolean isTrue = true;
String message = "Hello World";

In this example, we declare four variables of different data types and initialize them with values.

Control Structures

Control structures are used to control the flow of a program. These structures allow you to execute certain blocks of code based on a condition. Here are some of the common control structures in Java:

if-else statements – used to execute a block of code if a condition is true, or another block of code if the condition is false
for loops – used to execute a block of code repeatedly a certain number of times
while loops – used to execute a block of code repeatedly as long as a condition is true
switch statements – used to execute different blocks of code depending on the value of a variable

Here is an example of an if-else statement:

int num = 10;

if (num % 2 == 0) {
    System.out.println(num + " is even");
} else {
    System.out.println(num + " is odd");
}

In this example, we use the modulo operator to determine if the variable “num” is even or odd. If “num” is divisible by 2 with no remainder, we print “num is even”. Otherwise, we print “num is odd”.

Here is an example of a for loop:

for (int i = 0; i < 5; i++) {
    System.out.println("i is " + i);
}

In this example, we use a for loop to print the value of the variable “i” five times. The for loop initializes the variable “i” to zero, increments it by one on each iteration, and stops when “i” reaches five.

Classes and Objects

In Java, everything is organized into classes and objects. A class is a blueprint for creating objects, while an object is an instance of a class. Each object has its own set of characteristics and behaviors.

Here is an example of a class definition:

public class Rectangle {
    int width;
    int height;

    public int getArea() {
        return width * height;
    }
}

In this example, we define a class called “Rectangle” which has two instance variables called “width” and “height”. We also define a method called “getArea()” which calculates and returns the area of the rectangle.

Here is an example of how to create an instance of the “Rectangle” class:

Rectangle rect = new Rectangle();
rect.width = 10;
rect.height = 20;
int area = rect.getArea();

In this example, we create a new instance of the “Rectangle” class using the “new” keyword. We then set the values of the “width” and “height” variables and call the “getArea()” method to calculate the area of the rectangle.

Conclusion

This tutorial has covered the basics of Java programming including installing Java, creating your first Java program, variables and data types, control structures, and classes and objects. Java is a powerful programming language that can be used to create a wide variety of applications. By mastering the fundamentals covered in this tutorial, you’ll be well on your way to becoming a skilled Java developer.

Let's dive deeper into some of the topics covered in this Java tutorial. First, we'll take a look at variables and data types.

Variables and Data Types

Variables are used to store data in a program. In Java, variables must be declared with a specific data type. Here is a list of some common data types in Java:

boolean – represents true or false values
byte – represents a small integer value (-128 to 127)
short – represents a small integer value (-32768 to 32767)
int – represents an integer value (-2147483648 to 2147483647)
long – represents a long integer value (-9223372036854775808 to 9223372036854775807)
float – represents a floating-point value (up to 7 digits)
double – represents a floating-point value (up to 16 digits)
char – represents a single character value (e.g. 'a', 'b', 'c')
String – represents a sequence of characters (e.g. "Hello World")

Variables can be assigned a value when they are declared, or they can be assigned a value later on in the program. Here's an example of how to declare and initialize variables in Java:

int num1 = 5;
float num2 = 3.14f;
double num3 = 3.141592653589793238;
char character = 'a';
String message = "Hello World!";

In this example, we declare and initialize variables of different data types.

Control Structures

Control structures are used to control the flow of a program. They allow you to execute certain blocks of code based on a condition. Here are some of the common control structures in Java:

if-else statements – used to execute a block of code if a condition is true, or another block of code if the condition is false
for loops – used to execute a block of code repeatedly a certain number of times
while loops – used to execute a block of code repeatedly as long as a condition is true
switch statements – used to execute different blocks of code depending on the value of a variable

Here's an example of an if-else statement:

int num = 10;

if (num % 2 == 0) {
    System.out.println(num + " is even");
} else {
    System.out.println(num + " is odd");
}

Here's an example of a for loop:

for (int i = 0; i < 5; i++) {
    System.out.println("i is " + i);
}

Classes and Objects

Here's an example of a class definition:

public class Rectangle {
    int width;
    int height;

    public int getArea() {
        return width * height;
    }
}

Here's an example of how to create an instance of the “Rectangle” class:

Rectangle rect = new Rectangle();
rect.width = 10;
rect.height = 20;
int area = rect.getArea();

Conclusion

In this Java tutorial, we covered the basics of Java programming including installing Java, creating your first Java program, variables and data types, control structures, and classes and objects. By mastering these fundamental concepts, you'll be well on your way to becoming a skilled Java developer. Java is a powerful programming language that can be used to create a variety of applications, from simple console-based programs to complex web applications and enterprise systems.

java tutorialspoint with code examples

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Sricharan S

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