ArrayLists

ArrayLists

Resizable-array implementation of the List interface.
1. is an abstraction from programmer manipuplation of Arrays
2. part of Collections API
Implements all optional List operations
elements can be any object type and null
1. uses generics<T>
create new ArrayList object
1. ArrayList<String> list = new ArrayList<String>()
2. deafault size at creation is 10. can specify required size as constructor parameter
3. specify class name of objects it will hold in <>. can use empty <> after new.
4. Array is used as underlying hidden data structure
size increases automatically if add to full arraylist
METHODS
1. size: number of indices with elements
  1. int x = list.size()
2. remove element
  1. remove & return element at index i : E elem=list.remove(i);
  2. remove 1st match of element e: boolean b = list.remove(e);
  3. remove all elements: list.clear();
3. add element
  1. add element at end: list.add("something")
  2. insert at position of index: list.add(i, elem)
4. replace element: list.set(index, "something else");
5. get element at index i: E e= list.get(i);
6. list.contains(e)
7. list.isEmpty();
for-each or enhanced for loop can be used
ArrayList vs Array
1. AL: less efficient; not have convenient[ i] use; base type must be a class, not primitive(can use wrappers);
2. A: can't change in size - AL grow/shrink during use; A: need to keep cnt of elements in it- AL: does this auto; A: have NO methods - AL: powerful methods for manipulation

Zusammenfassung der Ressource

	Erstellt von Eithne O'Sullivan vor fast 7 Jahre