Java 5 introduced a nice utility called java.util.Scanner which is
capable to read input form command line in Java. Using Scanner is nice
and clean way of retrieving user
input from console or command line. Scanner can accept InputStream, Reader or simply
path of file from where to read input. In order to reading from command line we
can pass System.in into Scanner's constructor as
source of input. Scanner offers several benefit over classical BufferedReader
approach, here are some of benefits of using java.util.Scanner for
reading input from command line in Java:
1) Scanner supports regular
expression, which gives you power to read only matching pattern from input.
2) Scanner has methods like nextInt(), nextFloat() which can
be used to read numeric input from command line and can be directly used in
code without using Integer.parseInt() or any other parsing logic to convert
String to Integer or String
to double for floating point input.
Reading input from command line should be the first few thing which new
Java programmer should be taught as it help them to write interactive program and
complete programming exercise like checking
for prime number, finding
factorial of number, reversing
String etc. Once you are comfortable reading input from command line you
can write many interactive Java application without learning in GUI technology like Swing
or AWT.
Java program to read input from command prompt in Java
Here is sample code example of How to read input from command line or
command prompt in Java using java.util.Scanner class:
import java.io.IOException;
import java.util.Scanner;
public class ReadInputScannerExample {
public static void main(String args[]) throws IOException {
Scanner scanner = new Scanner(new InputStreamReader(System.in));
System.out.println("Reading input from console using Scanner in Java ");
System.out.println("Please enter your input: ");
String input = scanner.nextLine();
System.out.println("User Input from console: " + input);
System.out.println("Reading int from console in Java: ");
int number = scanner.nextInt();
System.out.println("Integer input: " + number);
}
}
Output:
Reading input from console using Scanner in Java
Please enter your input:
number
User Input from console: number
Reading int from console in Java:
1232
Integer input: 1232
import java.util.Scanner;
public class ReadInputScannerExample {
public static void main(String args[]) throws IOException {
Scanner scanner = new Scanner(new InputStreamReader(System.in));
System.out.println("Reading input from console using Scanner in Java ");
System.out.println("Please enter your input: ");
String input = scanner.nextLine();
System.out.println("User Input from console: " + input);
System.out.println("Reading int from console in Java: ");
int number = scanner.nextInt();
System.out.println("Integer input: " + number);
}
}
Output:
Reading input from console using Scanner in Java
Please enter your input:
number
User Input from console: number
Reading int from console in Java:
1232
Integer input: 1232
Just note that java.util.Scanner nextInt() will throw
"Exception in thread "main" java.util.InputMismatchException"
exception if you entered String or character data which is not number while
reading input using nextInt(). That’s all on how to read user
input from command line or command prompt in Java.
Related Java programming tutorials for beginners
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