Let's say you have a Groovy class
 
import java.util.concurrent.*
 
class NewGroovyClass {
    static void main(args) {
        
    }
}


Now stay in editor and hit Ctrl Space Bar to import ConcurrentHashMap. This is the result:
import java.util.concurrent.*
import java.util.concurrent.ConcurrentHashMap
 
class NewGroovyClass {
    static void main(args) {
        ConcurrentHashMap map;
    }
}

The editor doesn't respect wildcard imports