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Learn about Java ArrayList class, its properties, constructors, main methods, and how to effectively use it to store and manage collections of elements in Java programming.
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Programming II (CS300)Chapter 02: Using ObjectsJava ArrayList Class Mouna KACEM mouna@cs.wisc.edu Spring 2019
Java ArrayList Class Iterable extends • Java ArrayList Class inJava.utilpackage • uses a dynamic array for storing a set of elements • inherits AbstractList class and implements List interface • Main Properties • Java ArrayList class can contain duplicate elements • Java ArrayList class maintains insertion order • Java ArrayList allows random access • The dynamic array works at the index basis Collection extends List implements AbstractList extends ArrayList https://docs.oracle.com/javase/8/docs/api/java/util/ArrayList.html
Java ArrayList Class • Constructors • ArrayList list1 = new ArrayList(); //creating an empty ArrayList • ArrayList<String> list2 = new ArrayList<String>(); //creating an empty ArrayList of elements of type String • the type of elements is specified in angular braces • ArrayList list2 is forced to have only specified type of objects in it (here String). • Adding another type of object, results in a compile time error • ArrayList(Collection c) • build an array list that is initialized with the elements of the collection c. • ArrayList(int capacity) • build an array list that has the specified initial capacity.
Java ArrayList Class • Main Methods (1) • boolean add(Object o) • used to append the specified element to the end of a list. • void add(int index, Object element) • insert the specified element at the specified position index in a list. • booleanaddAll(Collection c) • append all of the elements in the specified collection to the end of this list, in the order that they are returned by the specified collection's iterator. • booleanaddAll(int index, Collection c) • used to insert all of the elements in the specified collection into this list, starting at the specified position.
Java ArrayList Class • Main Methods (2) • intindexOf(Object o) • used to return the index in this list of the first occurrence of the specified element, or -1 if the List does not contain this element. • intlastIndexOf(Object o) • return the index in this list of the last occurrence of the specified element, or -1 if the list does not contain this element.
Java ArrayList Class • Main Methods(3) • void clear() • remove all of the elements from this list. • Object[] toArray() • used to return an array containing all of the elements in this list in the correct order. • Object clone() • used to return a shallow copy of an ArrayList.