Create String list in Groovy

Question

The following code in Groovy adds GString s to the list:

List<String> args = [ 'cmd', "-Dopt=${value}" ]

When I create a ProcessBuilder with this list, I get a ClassCastException . What's a groovy way to coerce the list elements to the correct type?

Answer 1

Or, you can do:

List<String> args = [ 'cmd', "-Dopt=${value}"] as String[]

or

List<String> args = [ 'cmd', "-Dopt=${value}"]*.toString()

---

actually, why are you using ProcessBuilder out of interest? Groovy adds ways to do process management , and even adds three execute methods to List

You can do (this is on OS X or Linux):

def opt = '-a'

println( [ 'ls', "$opt" ].execute( null, new File( '/tmp' ) ).text )

which prints out the files in my /tmp folder

Answer 2

Try

List<String> args = [ 'cmd', "-Dopt=${value}".toString() ]

because the later is a GString .

Answer 3

I did a test:

def value = "abc"
List<String> args = [ 'cmd', "-Dopt=${value}"];

System.out.println (args.getClass());

System.out.println (args.get(0).getClass());
System.out.println (args.get(1).getClass());

The output was:

class java.util.ArrayList
class java.lang.String
class org.codehaus.groovy.runtime.GStringImpl

Changing the code a bit to be:

def value = "abc"
List<String> args = [ 'cmd', "-Dopt=${value}".toString()];

System.out.println (args.getClass());

System.out.println (args.get(0).getClass());
System.out.println (args.get(1).getClass());

produced this:

class java.util.ArrayList
class java.lang.String
class java.lang.String

Should do the trick, but I'm not 100% sure this is the best way to do it.