Lecture 2 - How to Take Input From User in Java

How to Take Input From User in Java?

In this lesson we will learn that how to take input from user in Java but before taking input from user we must learn that 'what is a variable in programming languages?' as we will need variable while taking input from user.

IMPORTANT:
👉No programming experience is required for this tutorial but if you have some programming experience in some other programming languages then obviously it will be beneficial.

👉 It is strongly recommended to watch the youtube channel for better understanding of the topics/concepts discussed through out in this tutorial.

What does variable mean in programming languages?

In programming languages, a variable is a symbolic name or identifier that represents a storage location in memory. Variables are used to store and manipulate data within a program. Each variable has a name and a data type associated with it.

Here are some key characteristics of variables in programming languages:

• Name/Identifier: A variable is given a name that programmers use to refer to it. Variable names are typically chosen to be descriptive and meaningful, so they convey the purpose or content of the data they store. Variable names must adhere to naming conventions and rules defined by the programming language. In Java, we use camel convention to define a variable. Click here to see different conventions being used in Java programming.
• Data Type: Every variable has a data type that defines the kind of data it can hold. Common data types include integers, floating-point numbers, characters, and more complex types like arrays, objects, and custom data structures. The data type of a variable determines the range of values it can store and the operations that can be performed on it. Click here to see data types in Java.
• Value: A variable can hold a specific value of its data type. You can assign a value to a variable, and you can change that value as the program runs.
• Memory Location: Variables represent a location in the computer's memory where the data is stored. When you declare a variable, the programming language sets aside memory space to store its data.
• Scope: Variables can have different scopes, which define where in the program the variable is accessible. For example, some variables may be local to a specific function or block of code, while others may have global scope, meaning they can be accessed from anywhere in the program.
• Lifetime: Variables have a lifetime that starts when they are created (usually when they are declared) and ends when they go out of scope or are explicitly destroyed. Automatic variables (local variables) have a lifetime tied to their scope, while dynamic memory allocation can be used to create variables with a longer lifetime.

Here's an example in Java to declare and use a variable:

int age; // Declaration of an integer variable named 'age' age = 30; // Assigning a value to the 'age' variable System.out.println("Age: " + age); // Printing the value of 'age'

Scanner Class in Java

In Java, you can take input from the user using the Scanner class, which is a part of the java.util package. Here's a step-by-step guide on how to take input from the user in Java:

1. Import the Scanner Class: To use the Scanner class, you need to import it at the beginning of your Java program. Add this line at the top of your Java file:
   import java.util.Scanner;
2. Create a Scanner Object: Next, create a Scanner object to read input from the user. You can do this in your main method or any other method where you want to take input. Here's how you create a Scanner object:
   Scanner scanner = new Scanner(System.in);
3. Read User Input: You can use various methods provided by the Scanner class to read input of different data types (e.g., integers, floating-point numbers, strings, etc.). Here's an example of reading a line of text from the user:
   System.out.print("Enter your name: "); String userInput = scanner.nextLine();
   
   If you want to read an integer, you can use nextInt():
   System.out.print("Enter your age: "); int age = scanner.nextLine();
   
   You can similarly use nextDouble() for floating-point numbers and other methods for different data types.

Here's a complete example demonstrating variables and use of Scanner class.

package example; import java.util.Scanner; public class Example { public static void main(String[] args) { Scanner input = new Scanner(System.in); System.out.print("Enter your first name: "); String fname=input.next(); //.next() is used for input string having one word System.out.println("Your first name is "+fname); System.out.print("Enter your full name: "); String name=input.nextLine(); //.nextLine() is used for input string having more than one words System.out.println("Your full name is "+name); } }

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