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Programming in Java Netbeans - A Step by Step Tutorial for Beginners: Lesson 5

Danson Wachira is a certified Trainer in Computer Science, Information Technology and related studies.

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Lesson 5: Working with user inputs in Java

java-programming-a-step-by-step-tutorial-for-beginners-lesson-5

Welcome to lesson 5 of Programming in Java. In Lesson 4 we learnt how to work with variables in Java and how to manipulate computer memory using variables. We also saw the use of different data types (int, double, float, String and char) in Java.

For this lesson, you will need to create a new class in myfirstprogram package. So, right click the package myfirstprogram, select New option from the menu and then select Java Class.


java-programming-a-step-by-step-tutorial-for-beginners-lesson-5

Let us call the new class UserInputs so, from the New Java Class window that will appear, enter UserInputs as the Class Name. Click Finish.

java-programming-a-step-by-step-tutorial-for-beginners-lesson-5

Now, delete all the comments in the code editor window as we did earlier and then include the “main” method in your class. Your code editor window should look like shown below:

java-programming-a-step-by-step-tutorial-for-beginners-lesson-5

As I mentioned earlier, Java contains a lot of functions or methods that are really useful to a programmer. These methods are written to accomplish a specific task that you may need to execute in your applications.

Related methods are grouped together and stored as a class. Related classes are stored in a package in Java library. When we want to use a certain method in Java, we reference its package and then the class into which it belongs.

One of the useful classes that handle inputs from a user in Java is the Scanner class. The Scanner class is located in the util (utility) package of the Java library. To use the Scanner class, we use the keyword import to reference it in our code, see below.

import java.util.Scanner;

The above statement tells Java that you want to use the Scanner class located in the util package of the java library. To use the class, we create new object of the class. This object work as the link between our code and the class and so we can be able to access the functions of the class from our code. We create the new object by using the following code:

Scanner user_input = new Scanner( System.in );

Notice that instead of creating an int variable or a String variable, we are creating a Scanner variable. We have called our Scanner variable user_input. After an equals sign, we have the keyword new. The keyword new is used to create new objects from a class. Here, we are creating an object from the Scanner class. In between the brackets we are specifying that the object is for a system input and we show this by including System.in inside the brackets.

To get the inputs from the user, we are going to use our new object, user_input, to call one of the many input methods available in the Scanner class. We’ll use the next method. This method gets the next string of text that a user types on the keyboard. It is one of the many methods in Scanner class. As you type next in the code editor you’ll see a list of other available methods.

Scanner user_input = new Scanner( System.in );

String user_name; user_name = user_input.next( );

Before we take the user name as input, we’ll add another statement to ask the user to enter the input. We have also created a String variable called user_name to store that input.

Scanner user_input = new Scanner( System.in );

String user_name;

System.out.print("Enter your name: ");

user_name = user_input.next( );

Notice that we have used print instead of println like we did earlier. The difference between the two is that println makes the cursor to move to a new line after the output, but with print the cursor stays on the same line. Let us now add our popular method to output the user input on the output window.

Scanner user_input = new Scanner( System.in );

String user_name;

System.out.print("Enter your name: ");

user_name = user_input.next( );

System.out.println("Your name is: " + user_name);

You code editor window should now look like shown below:

java-programming-a-step-by-step-tutorial-for-beginners-lesson-5

To run your program, go to the project window, right click your program and select Run File

java-programming-a-step-by-step-tutorial-for-beginners-lesson-5

When you run the program, Java will pause and ask you to enter your name, enter a name of your choice and press enter. You should be able to see the output as shown below:

java-programming-a-step-by-step-tutorial-for-beginners-lesson-5

Exercise: Modify your code so that you can input sir name and family name.

In the next lesson, we shall look on how to use Java Option panes for input and outputs purposes.


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