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June 14, 2010

Groovy Goodness: Expand or Unexpand Space or Tab Delimited Text

Groovy 1.7.3 adds new functionality to the String class. For example we can use the expand() method to expand tabs in a String to spaces with a default tab stop size of 8. We can use a parameter to use a different tab stop size. But we can also go the other way around.

So if we have a tabular text based on spaces we can convert the String to a tab separated String. Here the default tab stop size is also 8, but we can use the parameter to define a different tab stop size.

// Simple ruler to display 0 up to 30
def ruler = (0..30).inject('\n') { result, c -> 
    result += (c % 10) 

def stringWithTabs = 'Groovy\tGrails\tGriffon'

println ruler
println stringWithTabs.expand()  // default tab stop is 8
println stringWithTabs.expand(10)  // tab stop is 10

// Output:
// 0123456789012345678901234567890
// Groovy  Grails  Griffon
/ /Groovy    Grails    Griffon

assert 'Groovy  Grails  Griffon' == stringWithTabs.expand()
assert 'Groovy    Grails    Griffon' == stringWithTabs.expand(10)

def stringWithSpaces = 'Hubert  Klein   Ikkink'
def stringWithSpaces10 = 'Hubert    Klein     Ikkink'
println ruler
println stringWithSpaces
println stringWithSpaces10

// Output:
// 0123456789012345678901234567890
// Hubert  Klein   Ikkink
// Hubert    Klein     Ikkink

assert 'Hubert\tKlein\tIkkink' == stringWithSpaces.unexpand()
assert 'Hubert\tKlein\tIkkink' == stringWithSpaces10.unexpand(10)