Is there a Java 1.5 equivalent to the Predicate<T> methods in .Net?

Question

Specifically, I'm looking for similarly clean notation to the Collection<T>.TrueForAll / Exists, etc.

It feels smelly to have to write a foreach loop to inspect the return of a method on each object, so I'm hoping there's a better Java idiom for it.

Answer 1

Predicates are provided in the Google Collections library.

Answer 2

Functional Java provides first-class functions. A predicate is expressed as F<T, Boolean>. For example, here's a program that tests an array for the existence of a string that is all lowercase letters.

import fj.F;  
import fj.data.Array;  
import static fj.data.Array.array;
import static fj.function.Strings.matches;

public final class List_exists {  
  public static void main(final String[] args) { 
    final Array<String> a = array("Hello", "There", "how", "ARE", "yOU?");  
    final boolean b = a.exists(matches.f("^[a-z]*$"));  
    System.out.println(b); // true
  }  
}