find(groovy.lang.Closure closure) and findAll(groovy.lang.Closure closure) methods are really useful. It would be also good to have List#indexOf(groovy.lang.Closure closure) List#indexOf(int startIndex, groovy.lang.Closure closure) // startIndex tells from which index to start looking int[] List#indicesOfAll(groovy.lang.Closure closure) // return type may also be a List<Integer> or whatever List#lastIndexOf(groovy.lang.Closure closure) in the groovy jdk as it is sometimes important to know where the elements fullfilling the given condition are in the list.