Java Notes

Collections Class

The java.util.Collections class contains static utility methods for manipulating collections.

Some useful Collections methods

Assume the following declarations have been made, where T is a class or interface type.

   int i; 
   List<? extends T> list;
   List<T> listT;
   List<?> listO;
   Comparator<? super T> comp; 
   T key; 
   T t;
   Object obj; 
   Collection<? extends T> coll;

Returns	Method	Action
Rearranging - Sorting, Shuffling, . . .
	`sort(listT)`	Sorts `listT`. Elements must be Comparable<T>. Stable, O(N log N).
	`sort(listT, comp)`	Sorts `listT` using a comparator.
	`shuffle(listO)`	Puts the elements of `listO` in random order.
	`reverse(listO)`	Reverses the elements of `list`.
Searching
`i =`	`binarySearch(list, key)`	Searches in `list` for `key`. Elements must implement Comparable<T>. Returns index of element or negative value if not found. See Binary Search.
`i =`	`binarySearch(list, key, comp)`	Searches in `list` for `key` using Comparator comp. Returns index of element or negative value if not found. See Binary search.
`t =`	`max(coll)`	Returns maximum valued Comparable object in the Collection `coll`.
`t =`	`max(coll, comp)`	Returns maximum valued object in the Collection `coll` using Comparator `comp`.
`t =`	`min(coll)`	Returns minimum valued Comparable object in the Collection `coll`.
`t =`	`min(coll, comp)`	Returns minimum valued object in the Collection `coll` using Comparator `comp`.

There are many more methods in Collections, but the above are a good start.

Copyleft 2006 Fred Swartz MIT License

Related Tags for Java: Collections Class:

«Previous Index Next»