In this post three ways are given to read user input from keyboard (console) in Java-
- First way uses the
InputStreamReaderwrapped in a BufferedReader. - Second way to read input from console uses the
Scannerclass from Java 5. - Third way uses the
System.consolewhich was introduced in Java 6.
Read input from console in Java using BufferedReader
public class ReadFromConsole {
public static void main(String[] args) {
// Using BufferedReader
System.out.print("Please enter user name : ");
BufferedReader bufferRead = new BufferedReader(new InputStreamReader(System.in));
String s;
try {
s = bufferRead.readLine();
System.out.println("You entered- " + s);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
Output
Please enter user name : netjs You entered- netjs
In the program you can see that an InputStreamReader is wrapped with in a BufferedReader to read text from a character-input stream.
InputStreamReader wraps System.in where in is a field in a System class. in is the "standard" input stream. This stream is already open and ready to supply input data. Typically this stream corresponds to keyboard input or another input source specified by the host environment or user.
Read input from console using Scanner
Scanner class, added in Java 5 is another option to read input from console in Java. A Scanner breaks its input into tokens using a delimiter pattern, which by default matches whitespace. nextLine() method of the Scanner class advances this scanner past the current line and returns the input that was skipped.
Scanner class also has methods for different data types like nextInt(), nextDouble(), nextFloat() etc.
public class ReadFromConsole {
public static void main(String[] args) {
// Using Scanner
System.out.print("Please enter user name : ");
Scanner scanIn = new Scanner(System.in);
String scanLine = scanIn.nextLine();
System.out.println("You entered- " + scanLine);
System.out.println("Entered int value- " + scanIn.nextInt());
System.out.println("Entered float value- " + scanIn.nextFloat());
scanIn.close();
}
}
Output
Please enter user name : nets You entered- nets 3 78.90 Entered int value- 3 Entered float value- 78.9
Read input from console using System.console
console method in System class returns the unique Console object associated with the current Java virtual machine, if any.
A word of caution, if running the code from eclipse, System.console() will throw null pointer exception.
Please follow this discussion to know more about this exception- http://stackoverflow.com/questions/104254/java-io-console-support-in-eclipse-ide
public class ReadFromConsole {
public static void main(String[] args) {
//Using System.console()
String username = System.console().readLine("Please enter user name : ");
System.out.println("You entered : " + username);
}
}
Output
Please enter user name : netjs You entered : netjs
That's all for this topic How to Read Input From Console in Java. If you have any doubt or any suggestions to make please drop a comment. Thanks!
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