Question

I would like to be able to test if a List contain an object with a given key-value

For example, I would like to do something like Iterables.contains(l2, “lname”, “Jordan”)); instead of having to create all other Map objects like below in l2

//List<String> l = Arrays.asList("Mickael", "Jordan", "His Airness");
//System.out.println(Iterables.contains(l, "Jordan"));

Map<String, String> p1 = new HashMap<String, String>();
p1.put("fname", "Mickael");
p1.put("lname", "Jordan");
p1.put("nname", "His Airness");

Map<String, String> p2 = new HashMap<String, String>();
p2.put("fname", "Paul");
p2.put("lname", "Pierce");
p2.put("nname", "The Truth");
List<Map<String, String>> l2 = Arrays.asList(p1, p2);
Map<String, String> p3 = new HashMap<String, String>();
p3.put("fname", "Mickael"); //
p3.put("lname", "Jordan");
p3.put("nname", "His Airness"); //
System.out.println(Iterables.contains(l2, p3));

I’d like to know if there’s such guava’s function, and not doing a loop on l2 and testing each elt.get(“lname”)

Edit

3 solutions answered: trying to see which one is more perfomant

System.out.println(Iterables.any(l2, withEntry("lname", "Jordan"))); //@axtavt
System.out.println(has("lname", "Jordan")); //@JB
System.out.println(Iterables.any(l2, new KeyValuePredicate("lname", "Jordan"))); //@JB

public static Boolean has(final String key, final String value) {
    return Iterables.any(l2, new Predicate<Map<String, String>>() {
        @Override
        public boolean apply(Map<String, String> input) {
            return input.get(key).equals(value);
        }
    });
}

public static Predicate<Map<String, String>> withEntry(final String key, final String value) {
    return new Predicate<Map<String, String>>() {
        public boolean apply(Map<String, String> input) {
            return value.equals(input.get(key));
        }
    };
}

class KeyValuePredicate implements Predicate<Map<String, String>>{
private String key;
private String value;
public KeyValuePredicate(String key, String value) {
    super();
    this.key = key;
    this.value = value;
}
@Override
public boolean apply(Map<String, String> arg0) {
    // TODO Auto-generated method stub
    return arg0.get(key).equals(value);
}

}

Answer 1

return Iterables.any(l2, new Predicate<Map<String, String>>() {
    @Override
    public boolean apply(Map<String, String> input) {
        return input.get("lname").equals("Jordan");
    }
});

But you’re using maps when you should use objects with properties.

Of course, if you need to do that multiple times, with various properties, you should transform the predicate into a non-anonymous, reusable class:

return Iterables.any(l2, new KeyValuePredicate("lname", "Jordan"));