org.mdiutil.util.partialset

The partialset package contains additional classes which provides partial ordering sets. The work with the Java util package.

Overview

The PartiallyOrderedHashSet and PartiallyOrderedTreeSet classes are Set implementations where the order of the elements in the Set is a partial order:

• The PartiallyOrderedHashSet class specify a Set where some elements in the Set are ordered explictly
• The PartiallyOrderedTreeSet class specify a Set where some elements in the Set are ordered explictly. The other elements are ordered by their natural order

Both the PartiallyOrderedHashSet and PartiallyOrderedTreeSet classes implement the PartiallyOrderedSet interface.

Adding an explicit ordering between two elements

The PartiallyOrderedSet interface has several methods to handle an explicit order between two elements:

• The PartiallyOrderedSet.setOrdering(Object first, Object second) specifies that the second object must be iterated after the first object
• The PartiallyOrderedSet.unsetOrdering(Object first, Object second) removes the explicit ordering between the two objects
• The PartiallyOrderedSet.hasOrdering(Object first, Object second) return true if there is an explicit ordering between the two objects

Example

   PartiallyOrderedHashSet<String> set = new PartiallyOrderedHashSet<>();
   set.add("A");
   set.add("B");
   set.add("C");      
   set.add("D");
      
   set.setOrdering("D", "B"); 
   set.setOrdering("C", "A");
   set.setOrdering("A", "D"); 
      
   Iterator<String> it = set.iterator();
      
   String elt = it.next(); // elt is "C"
   elt = it.next(); // elt is "A"
   elt = it.next(); // elt is "D" 
   elt = it.next(); // elt is "B"