List of common methods for list map set

List Common methods:

• Default add: List.add (e);

• Specify the subscript to add (after adding the element after subscript, move one bit backwards): List.add (index,e);

• Get the number of elements in the set: List.size ();

• Returns whether deleted: List.remove (e);

• Delete the element that specifies the subscript directly (delete only the first matching element found): List.remove (index);

• Replace element (replaces the element with the specified subscript): List.set (index,e);

• remove element: List.get (index);

• Empty collection: List.clear ();

• Determines whether an element exists in the collection (there is a return of true, there is no return false): List.contains (e);

• Two objects must be equal: List.equals (LIST2);

• Two objects are not necessarily equal: list.hashcode () = = List2.hashcode ();
  (The Equals method of two equal objects must be true, but two hashcode equal objects are not necessarily equal.)

• The element exists then returns the subscript of the first element found, and returns -1:list.indexof (e) If it does not exist;

• The element exists then returns the subscript of the last element found, and returns -1:list.lastindexof (e) If it does not exist;

• Determines whether the collection is empty (null returns TRUE, non-null returns FALSE): List.isEmpty ();

• Returns the Iterator Collection object: List.iterator ();

  • list<string> list = new arraylist<string> ();
    List.add ("1234");
    List.add ("12345");
    List.add ("12346");
    List.add ("12347");
    List.add ("12348");
    Iterator<string> it = List.iterator ();//Traversal
    while (It.hasnext ()) {
    System.out.println (It.next ());
    }

• Converts a collection to a string: list.tostring ();

• To convert a collection to an array:
  Default type: List.toarray ();
  Specifies the type (objects is an array object of the specified type and assigns the transformed array to the objects array): List.toarray (objects);

• List Traversal Method
• public static void Main (string[] args) {
  List<string> list=new arraylist<string> ();
  List.add ("AA");
  List.add ("BB");
  List.add ("CC");
  List.add ("DD");
  The first traversal method of the list
  for (String str:list) {
  System.out.print (str+ "");
  Print AA BB cc DD
  }
  System.out.println ();
  The second traversal method of list
  for (int i=0;i<list.size (); i++) {
  if (I!=list.size ()-1) {
  System.out.print (List.get (i) + "");
  This remove (i) is removed from the printed
  List.remove (i);
  }else{
  System.out.print (List.get (i));
  }
  Print as AA cc
  }
  The third kind of traversal method for list
  System.out.println ();
  For (iterator<string> iterator=list.iterator (); Iterator.hasnext ();) {
  if (Iterator.hasnext ()) {
  System.out.print (Iterator.next () + "");;
  }else{
  System.out.print (Iterator.next ());;
  }
  }
  Print AA BB cc DD
  }

List of common methods for list map set