How to Read Characters in Java Using Scanner
The Scanner grade is used to read Coffee user input. Coffee Scanner is congenital into the java.util package, so no external libraries are needed to use it. Scanner reads text from standard input. This text is returned to the main programme so information technology tin be stored or otherwise manipulated.
Understanding how to get user input in Java is a crucial skill. For instance, say you are edifice an app with a sign-in grade. Y'all will need to handle user input to collect the login credentials for the user.
In Java, you can use the Scanner class to receive user input that y'all can then process in your program. This tutorial will talk over, using a few examples, how to utilize the Java Scanner class to receive user input.
Coffee Scanner Class
The Java Scanner form is used to collect user input. Scanner is office of the java.util package, then it can exist imported without downloading any external libraries. Scanner reads text from standard input and returns information technology to a programme.
In guild to piece of work with the Scanner class, you lot must first import it into your code. At that place are two ways you can exercise this:
- If yous merely demand to work with the coffee.util.Scanner class, you lot tin can import the Scanner class directly.
- If you are working with other modules in the java.util library, y'all may want to import the full library.
The following is the lawmaking for each of the above methods:
import java.util.Scanner; import java.util.*;
The first line of code imports the Scanner course. The 2nd line of lawmaking imports all the packages within the java.util library, including Scanner.
It'due south worth noting that in that location are other ways to receive user input data in Java. Y'all can apply Coffee's BufferedReader, InputStreamReader, DataInputStream, and Console classes.
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However, the Scanner class is the most popular method of collecting user input in Java. So, we volition be focusing on that course in this article.
Java User Input Syntax
You tin can collect user input using the Scanner class. The Scanner class reads text that a user inserts into the console and sends that text back to a program. Scanner is the primary method of collecting Coffee user input.
Afterward you import the Java Scanner form, you can starting time to use it to collect user input. Here is the syntax for the Java Scanner grade:
Scanner input = new Scanner(Arrangement.in); int number = input.nextInt();
In this case, nosotros created a variable chosen input that collects the next value the user inputs into the console. Then we created a variable chosen number that collects the value the user submits to the console.
Java User Input Case
For instance, suppose we are building an application for a local calculator shop that keeps track of their inventory.
The managing director asked united states of america to create a simple plan that she tin can use to add together items to the shop's inventory listing. The manager wants to be able to input two values: the name of the item and its quantity.
Hither'south the code we would use to create this program:
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import java.util.Scanner; course Main { public static void main(Cord[] args) { Scanner input = new Scanner(System.in); System.out.print("Product name: "); String product_name = input.next(); System.out.impress("Value entered: " + product_name); System.out.print("Quantity: "); int quantity = input.nextInt(); System.out.print("Value entered: " + quantity); } } The first input we accept the name of the item. This will be a string because the item names are text-based and use a variety of characters. In the code beneath, we define this string with the code: String product_name.
The side by side input is the quantity of the item. This will exist a number. In the code below, nosotros define this number with the code: int quantity, where int stands for integer.
When we run our code and insert a few example values, the programme returns the following response:
Production name: 15-inch MacBook Pro 2019
Value entered: 15-inch MacBook Pro 2019
Quantity: 7
Value entered: 7
As you can meet, our program collected the user'south input. It then returned to the console the value the user entered. This allows us to verify that our program is working.
How our Scanner Java Program Works
Let'south pause downwardly our lawmaking step-by-step.
- We import the Scanner library into our lawmaking so that we tin receive user input.
- Nosotros declare a class called Primary that stores the code for our plan.
- We initialize the Scanner course using Scanner input = new Scanner(Organisation.in); The input Java variable stores our initialized scanner.
- We impress out "Production proper noun: " to the console and ask the user to submit a product name using input.next();.
- We impress out to the console the product name the user submitted.
- We impress out Quantity: to the console and prompt the user to submit the quantity of the product in stock using input.nextInt();.
- We print out the value of the quantity variable to the panel.
Notice that we used dissimilar code to collect numbers and strings. When we collected the production proper name, we used input.adjacent();, and when nosotros nerveless the product quantity, we used input.nextInt();.
Java Scanner: Input Types
In our above case, we collected ii types of information from the user: a string and an integer. As mentioned, nosotros had to use different lawmaking to collect these types of data.
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Different types of data, like strings and integers, are collected using separate methods. Then, to collect a boolean, y'all'll use different code than yous would to collect a float.
Here is a table showing all the methods used to collect user input in Java using the Scanner class:
| Method | Type of Value the Method Collects |
| nextBoolean() | boolean |
| nextByte() | byte |
| nextDouble() | double |
| nextFloat() | float |
| nextInt() | int |
| nextLine() | String |
| nextLong() | long |
| nextShort() | brusque |
If you insert the wrong input blazon, your program will enhance an InputMismatchException. For instance, if yous try to insert a double into a field that collects Booleans, your programme will raise an exception.
Collecting a Boolean Value
Let's get back to the computer store. Suppose nosotros wanted to update our first programme and allow our computer store manager to input whether the production is on brandish or held in the stockroom.
To do so, we want to collect a new value called on_display that will shop input as a Boolean because information technology can have only 2 values: true or false.
Here's the code we could use to collect this data:
import java.util.Scanner; class Main { public static void main(String[] args) { Scanner input = new Scanner(System.in); Organization.out.print("Production name: "); String product_name = input.side by side(); Arrangement.out.print("Value entered: " + product_name); System.out.print("Quantity: "); int quantity = input.nextInt(); Organization.out.impress("Value entered: " + quantity); Organisation.out.print("On display: "); boolean on_display = input.nextBoolean(); System.out.impress("Value entered: " + on_display); } } When we run our lawmaking and insert a few example values, the program returns the following response:
Product name: xv-inch MacBook Pro 2019
Value entered: 15-inch MacBook Pro 2019
Quantity: 7
Value entered: seven
On display: truthful
Value entered: true
Our plan works in the same way equally our example higher up. However, this time we collect an additional value from the user: whether the product they inserted into the programme is on display. Nosotros use the nextBoolean() method to collect this value from the user. Then we print that value to the console.
Decision
You tin can use Java'southward Scanner class to collect input from a user. The Scanner form is capable of collecting a variety of data types from users, including short values, Strings, booleans, and others.
In this tutorial, using a few examples, we explored how to use the Java Scanner grade to collect user input. In improver, we discussed the different data types offered past the Scanner class that nosotros can use to collect user input.
To learn more well-nigh coding in Java, read our How to Lawmaking in Java guide.
Source: https://careerkarma.com/blog/java-input/
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