根据比较器求最小值

Question

I was wondering if there is a way to find the minimum or maximum of a collection using a comparator in the Apache commons-collection library. Something equivalent to this using Guava:

return Ordering.from(comparator).max(collection);

Answer 1

java.util.Collections has methods

max(Collection) // natural order
max(Collection, Comparator) // according to compare provided

min(Collection)   // natural order
min(Collection, Comparator)  // according to compare provided

Answer 2

Why not simply use the min and max methods of the Collection class?

Example:

  LinkedList<Integer> list = new LinkedList<Integer>();
  list.add(-15);  
  list.add(33);  
  list.add(-23);  
  list.add(11); 
  System.out.println("Max value: " + Collections.max(list,comparator)); 

Answer 3

like so:

Item getMax(Collection<Item> items, Comparator<Item> comparator) {
    Item temp = null;
    for(Item item : items) {
        if(temp == null || comparator.compare(temp, item) < 0)
            temp = item;
    }
    return temp;
}

Item getMin(Collection<Item> items, Comparator<Item> comparator) {
    Item temp = null;
    for(Item item : items) {
        if(temp == null || comparator.compare(temp, item) > 0)
            temp = item;
    }
    return temp;
}