Arraylist swap elements

Question

How do I swap the the first and last elements of an ArrayList  I know how to swap the elements of an array  setting a temporary value to store the first element  letting the first element equal the last element  then letting the last element equal the stored first element   int a   values 0   int n   values length  values 0    values n-1   values n-1    a    So for an ArrayList lt String gt  would it be like this   String a   words get 0   int n   words size    words get 0    words get n-1   words get n-1    a

User · Answer

You can use Collections swap List lt   gt  list  int i  int j

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Use like this  Here is the online compilation of the code  Take a look http   ideone com MJJwtc     public static void swap List list                          int i                          int j    Swaps the elements at the specified positions in the specified list   If the specified positions are equal  invoking this method leaves the list unchanged    Parameters      list - The list in which to swap elements      i - the index of one element to be swapped      j - the index of the other element to be swapped    Read The official Docs of collection  http   docs oracle com javase 7 docs api java util Collections html swap 28java util List  20int  20int 29  import java util    import java lang     class Main       public static void main String   args  throws java lang Exception                            create an ArrayList object         ArrayList words   new ArrayList               Add elements to Arraylist         words add  A            words add  B            words add  C            words add  D            words add  E             System out println  Before swaping  ArrayList contains       words                     To swap elements of Java ArrayList use        static void swap List list  int firstElement  int secondElement        method of Collections class  Where firstElement is the index of first       element to be swapped and secondElement is the index of the second element       to be swapped         If the specified positions are equal  list remains unchanged         Please note that  this method can throw IndexOutOfBoundsException if       any of the index values is not in range                     Collections swap words  0  words size   - 1            System out println  After swaping  ArrayList contains       words                  Oneline compilation example http   ideone com MJJwtc

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for  int i   0  i  lt  list size    i              if  i  lt  list size   - 1                if  list get i   gt  list get i   1                     int j   list get i                   list remove i                   list add i  list get i                    list remove i   1                   list add j                   i   -1

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In Java  you cannot set a value in ArrayList by assigning to it  there s a set   method to call   String a   words get 0   words set 0  words get words size   - 1    words set words size   - 1  a

[java] Arraylist swap elements

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