Data Structure in Java

All are obtained from JDK source code or Apache or Google jar package source code.

/**

* Reverses the order of the elements in the specified list. <p> * * This method runs in linear time. * * @ Param list the list whose elements are to be reversed. * @ Throws unsupportedoperationexception if the specified list or * Its list-iterator does not support the <tt> set </tt> method. */ Public static void Reverse (List <?> List) {int size = List. size (); If (size <reverse_threshold | list instanceof randomaccess) {for (INT I = 0, mid = size> 1, j = size-1; I <mid; I ++, j --) Swap (list, I, j);} else {listiterator FWD = List. listiterator (); listiterator REV = List. listiterator (size); For (INT I = 0, mid = List. size ()> 1; I <mid; I ++ ){ Object TMP = FWD. Next (); FWD. Set (rev. Previous (); rev. Set (TMP );}}} /** * Randomly permutes the specified list using a default source * Randomness. All permutations occur with approximately equal * Likelihood. <p> * * The Hedge "approximately" is used in the foregoing description because * Default source of randomness is only approximately an unbiased source * Of independently chosen bits. If it were a perfect source of randomly * Chosen bits, then the algorithm wowould choose permutations with perfect * Uniformity. <p> * * This implementation traverses the list backwards, from the last element * Up to the second, repeatedly swapping a randomly selected element * The "Current Position". elements are randomly selected from * Portion of the list that runs from the first element to the current * Position, inclusive. <p> * * This method runs in linear time. If the specified list does not * Implement the {@ link randomaccess} interface and is large, this * Implementation dumps the specified list into an array before shuffling * It, and dumps the shuffled array back into the list. This avoids * Quadratic behavior that wowould result from shuffling a "sequential * Access "list in place. * * @ Param list the list to be shuffled. * @ Throws unsupportedoperationexception if the specified list or * Its list-iterator does not support the <tt> set </tt> method. */ Public static void Shuffle (List <?> List) {shuffle (list, R);} Private Static Random R = New random (); /** * Randomly Permute the specified list using the specified source * Randomness. All permutations occur with equal likelihood * Assuming that the source of randomness is fair. <p> * * This implementation traverses the list backwards, from the last element * Up to the second, repeatedly swapping a randomly selected element * The "Current Position". elements are randomly selected from * Portion of the list that runs from the first element to the current * Position, inclusive. <p> * * This method runs in linear time. If the specified list does not * Implement the {@ link randomaccess} interface and is large, this * Implementation dumps the specified list into an array before shuffling * It, and dumps the shuffled array back into the list. This avoids * Quadratic behavior that wowould result from shuffling a "sequential * Access "list in place. * * @ Param list the list to be shuffled. * @ Param RND the source of randomness to use to shuffle the list. * @ Throws unsupportedoperationexception if the specified list or its * List-iterator does not support the <tt> set </tt> operation. */ Public static void Shuffle (List <?> List, random RND) {int size = List. size (); If (size <shuffle_threshold | list instanceof randomaccess) {for (INT I = size; I> 1; I --) Swap (list, I-1, RND. nextint (I);} else {object arr [] = List. toarray (); // shuffle array for (INT I = size; I> 1; I --) Swap (ARR, I-1, RND. nextint (I); // dump array back into list listiterator it = List. listiterator (); For (INT I = 0; I <arr. length; I ++) {It. next (); it. set (ARR [I]) ;}} /** * Swaps the elements at the specified positions in the specified list. * (If the specified positions are equal, invoking this method leaves * The list unchanged .) * * @ Param list the list in which to swap elements. * @ Param I the index of one element to be swapped. * @ Param J the index of the other element to be swapped. * @ Throws indexoutofboundsexception if either <tt> I </tt> or <tt> j </tt> * Is out of range (I & lt; 0 | I & gt; = List. Size () * | J & lt; 0 | J & gt; = List. Size ()). * @ Since 1.4 */ Public static void Swap (List <?> List, int I, Int J ){ Final list l = List; L. Set (I, L. Set (J, L. Get (I )));} /** * Swaps the two specified elements in the specified array. */ Private Static void Swap (Object [] arr, int I, Int J) {object TMP = arr [I]; arr [I] = arr [J]; arr [J] = TMP ;}.. to be continued