Groovy: read from console (STDIN, keyboard)

Reading from the Standard Input (aka. STDIN) which is by default connected to the keyboard is somewhere between Java and the dynamic languages in lightness.

Read from STDIN in Groovy

Reading from the Standard Input, normally the keyboard, is also quite easy.

System.in represents the Standard Input channel.

def defines a variable name. There is no need to declare the type of the variable.

println only takes one argument, so instead of passing a list of values we use the + operator to concatenate the values.

print "What is your name? "
def name = System.in.newReader().readLine()
println "Your name is " + name

Read from Console in Groovy

A shorter alternative is to use the Console object, but rumors say that it might not work inside an IDE. It works when running in the terminal.

def name = System.console().readLine 'What is your name? '
println "Your name is " + name

Converting string to Integer

When we read a value from the standard input it arrives as a string. It cannot be used in numerical operations even if the input looks like a number. In order to use it as a number we have to tell Groovy to treat it as a number. For example as an Integer. That's what "as Integer" is for in the next example:

Rectangular

See the rectangular exercise.

print "First number: "
def x = System.in.newReader().readLine() as Integer
print "Second number: "
def y = System.in.newReader().readLine() as Integer
println x * y

timestamp: 2018-05-27T09:00:01 tags:

• Console
• System
• readLine