Question

Consider a collection consisting of enum types. Is there some library method min (or max) which accepts this collection (or varargs) and returns the smallest/highest value?

EDIT: I meant the natural order of enums, as defined by their compare implementation of Comparable.

Answer 1

Enums implement Comparable<E> (where E is Enum<E>) and their natural order is the order in which the enum constants are declared.
You can use their default Comparable implementation to get the max and min constants as declared:

public enum BigCountries {
    USA(312), INDIA(1210), CHINA(1330), BRAZIL (190);

    private int population;

    private BigCountries(int population) {
        this.population = population;
    }

}

Then you can use:

BigCountries first = Collections.min(Arrays.asList(BigCountries.values())); // USA
BigCountries last = Collections.max(Arrays.asList(BigCountries.values()));  //BRAZIL

Probably, a faster way would be to use direct access to the array returned by the values() method:

BigCountries[] values = BigCountries.values();
System.out.println(values[0]); // USA;
System.out.println(values[values.length-1]); // BRAZIL;

Note that the parameter given to the enum has no effect in the ordering.