How do I get a Boolean value for a partial match using Groovy's regex?

Question

Groovy has a regular expression \"match operator\" (==~). The documentation says it returns a Boolean, but requires a \"strict match\". It does not define \"str

Answer 1

The 'foo-bar-baz' ==~ /bar/ is equal to "foo-bar-baz".matches("bar"), that is, it requires a full string match.

The =~ operator allows partial match, that is, it may find a match/matches inside a string.

Hence:

println('foo-bar-baz' ==~ /bar/) // => false
println('bar' ==~ /bar/)         // => true
println('foo-bar-baz' =~ /bar/)  // => java.util.regex.Matcher[pattern=bar region=0,11 lastmatch=]

See this Groovy demo

If you need to check for a partial match, you cannot avoid building a Matcher object:

use the find operator =~ to build a java.util.regex.Matcher instance

   def text = "some text to match"
   def m = text =~ /match/                                           
   assert m instanceof Matcher                                       
   if (!m) {                                                         
       throw new RuntimeException("Oops, text not found!")
   }

if (!m) is equivalent to calling if (!m.find())

Alternatively, you may use the ! twice to cast the result to correct Boolean value:

println(!!('foo-bar-baz' =~ /bar/))

Returns true.