What is the best way to remove the first element from an array

Question

I have  string array  String    and I need to remove the first item  How can I do that efficiently

User · Answer

To sum up  the quick linkedlist method   List lt String gt  llist   new LinkedList lt String gt  Arrays asList oldArray    llist remove 0

User · Answer

You can t do it at all  let alone quickly   Arrays in Java are fixed size   Two things you could do are    Shift every element up one  then set the last element to null  Create a new array  then copy it    You can use System arraycopy for either of these   Both of these are O n   since they copy all but 1 element   If you will be removing the first element often  consider using LinkedList instead   You can use LinkedList remove  which is from the Queue interface  for convenience   With LinkedList  removing the first element is O 1    In fact  removing any element is O 1  once you have a ListIterator to that position   However  accessing an arbitrary element by index is O n

User · Answer

An alternative ugly method      String   a    BLAH00001   DIK-11   DIK-2   MAN5       String   k Arrays toString a  split      2  1  split      0  split

User · Answer

The size of arrays in Java cannot be changed   So  technically you cannot remove any elements from the array   One way to simulate removing an element from the array is to create a new  smaller array  and then copy all of the elements from the original array into the new  smaller array   String   yourArray   Arrays copyOfRange oldArr  1  oldArr length     However  I would not suggest the above method   You should really be using a List lt String gt    Lists allow you to add and remove items from any index   That would look similar to the following   List lt String gt  list   new ArrayList lt String gt        or LinkedList lt String gt     list add  Stuff       add lots of stuff list remove 0      removes the first item

User · Answer

Keep an index of the first  live  element of the array  Removing  pretending to remove  the first element then becomes an O 1  time complexity operation

User · Answer

Simplest way is probably as follows - you basically need to construct a new array that is one element smaller  then copy the elements you want to keep to the right positions   int n oldArray length-1  String   newArray new String n   System arraycopy oldArray 1 newArray 0 n     Note that if you find yourself doing this kind of operation frequently  it could be a sign that you should actually be using a different kind of data structure  e g  a linked list  Constructing a new array every time is an O n  operation  which could get expensive if your array is large  A linked list would give you O 1  removal of the first element   An alternative idea is not to remove the first item at all  but just increment an integer that points to the first index that is in use  Users of the array will need to take this offset into account  but this can be an efficient approach  The Java String class actually uses this method internally when creating substrings

[java] What is the best way to remove the first element from an array?

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