Java User Input
The Scanner class is used to get user input and is the easiest way to read input in Java program. Java Scanner class permits the user to take input from the console. The class is belongs to java.util package. It is used to read the input of primitive types like int, double, long, short, float, and byte.
Syntax
Scanner sc=new Scanner(System.in);
The above statement creates a constructor of the Scanner class having System.in as an argument. it is going to read from the standard input stream of the program taking input from the console. The java.util package should be import while using Scanner class. It also converts the Bytes that is from the input stream into characters using the platform’s default charset.
The most widely used method is Scanner and I personally prefer it because of its simplicity and easy implementation, as well as its powerful utility to parse text into primitive data.
Advantages of Using Scanner
- Easy to use the Scanner class.
- Easy input of numbers (int, short, byte, float, long and double).
- Exceptions are unchecked which is more convenient. It is up to the programmer to be civilized, and specify or catch the exceptions.
- Is able to read lines, white spaces, and regex-delimited tokens
In order to use the Scanner class, create an object of the class and use any of the available methods found in the Scanner class documentation. In our example, we will use the nextLine() method, which is used to read Strings:
Example
import java.util.Scanner; // This statement is Import the Scanner class
class ExampleMain {
public static void main(String[] args) {
Scanner myObj = new Scanner(System.in); // This statement is Create a Scanner object
System.out.println("Enter username");
String userName = myObj.nextLine(); // This statement is Read user input
System.out.println("Username is: " + userName); // This statement is Output user input
}
}
OUTPUT
Enter username
Harun
Username is: Harun
If you are not well known what a package is, read our Java Packages/API Tutorial.
Input Types
In the example above, we used the nextLine() method, which is used to read Strings. To read other types, look at the table below:
| Method | Description |
| nextBoolean() | It is used to scan Reads a Boolean value from the user |
| nextByte() | It is used to scan Reads a byte value from the user |
| nextDouble() | It is used to scan Reads a double value from the user |
| nextFloat() | It is used to scan Reads a float value from the user |
| nextInt() | It is used to scan Reads an int value from the user |
| nextLine() | It is used to scan Reads a String value from the user |
| nextLong() | It is used to scan Reads a long value from the user |
| nextShort() | It is used to scan Reads a short value from the user |
| int nextInt() | It is used to scan the next token of the input as an integer. |
| nextBigInteger() | It is used to scan the next token of the input as a BigInteger. |
| nextBigDecimal() | It is used to scan the next token of the input as a BigDecimal. |
In the example below, we use different methods to read data of various types:
Example
import java.util.Scanner;
class ExampleMain {
public static void main(String[] args) {
Scanner myObj = new Scanner(System.in);
System.out.println("Enter name age and salary:");
String name = myObj.nextLine(); // This statement is String input
int age = myObj.nextInt(); // This statement is Numerical input
double salary = myObj.nextDouble();
System.out.println("Name: " + name); // This statement is Output input by user
System.out.println("Age: " + age);
System.out.println("Salary: " + salary);
}
}
OUTPUT
Enter name, age and salary:
Harun
22
40000
Name: Harun
Age: 22
Salary: 40000
Example of integer input from user. The following example allows user to read an integer form the System.in.
import java.util.*;
class ExampleMain
{
public static void main(String[] args)
{
Scanner sc= new Scanner(System.in); //System.in is a standard input stream
System.out.print("Enter first number: ");
int a= sc.nextInt();
System.out.print("Enter second number:");
int b= sc.nextInt();
System.out.print("Enter third number: ");
int c= sc.nextInt();
int d=a+b+c;
System.out.println("Total= " +d);
}
}
Output:
How to get input from user in Java
Example of String Input from user
Let’s see another example, in which we have taken string input.
import java.util.*;
class ExampleMain
{
public static void main(String[] args)
{
Scanner sc= new Scanner(System.in); //System.in is a standard input stream
System.out.print("Enter a string: ");
String str= sc.nextLine(); //This statement is read string
System.out.print("You have entered: "+str);
}
}
Output:
How to get input from user in Java. If you enter wrong input (for example, text in a numerical input), you will get an exception/error message ( such as “InputMismatchException”).