Guava Source Analysis--ordering

Needless to doubt, ordering definitely implements the Comparator<t> interface, which is used in comparison sorting in Java. Whereas the static method returns a type of ordering, the different ordering subclasses implement their own compare () method, as follows:

 Public Static extends Comparable> ordering<c> Natural () {  return (ordering<c>) naturalordering.instance;}

The implementation class has the following:

If the ordering subclass is constructed without arguments, it is only constructed as a singleton using the final static instance method, which is thread safe because there are no shared member variables.

Decoration mode in which the perfection is used. As an example, verify that:

list<integer> numbers = lists.newarraylist (null, 1, 3, 2, 5, 4, 6); List<Integer> sorted = ordering.natural (). Nullsfirst (). sortedcopy (numbers);  for (integer integer:sorted) {System.out.println (integer);}

Ordering.natural () returns the Naturalordering.instance object and then calls Nullfirst (), returning the new nullsfirstordering<s> (this); This is the Naturalordering.instance object at this point, and the Nullsfirstordering constructor method aggregates the ordering parent class, and when the Compare () method is overridden, the null sort logic is added after the decoration.

 @Override 
 public  int   compare (@Nullable t left, @Nullable T-right) { if  (left == right) { return  0;  if  (left = = null   return   Right_is_greater;  if  (right = = null   return   Left_is_greater;  return   Ordering.compare (left, right);} 

Finally ordering the parent class encapsulated in the way Sortedcopy (), in the call Arrays.sort (array, this) method, to decorate the ordering as the comparator incoming sort () method, Thus the perfect realization of the chain form of writing and calling rules.

The implementation of other sorting methods is not explained. Ordering the main analysis is the use of adorners

Guava Source Analysis--ordering