The ArrayList Class An ArrayList object stores a list of objects, and is often processed using a loop The ArrayList class is part of the java.util package.

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Presentation transcript:

The ArrayList Class An ArrayList object stores a list of objects, and is often processed using a loop The ArrayList class is part of the java.util package You can reference each object in the list using a numeric index An ArrayList object grows and shrinks as needed, adjusting its capacity as necessary Copyright © 2017 Pearson Education, Inc.

The ArrayList Class Index values of an ArrayList begin at 0 (not 1): 0 "Bashful" 1 "Sleepy" 2 "Happy" 3 "Dopey" 4 "Doc" Elements can be inserted and removed The indexes of the elements adjust accordingly Copyright © 2017 Pearson Education, Inc.

ArrayList Methods Some ArrayList methods: boolean add(E obj) void add(int index, E obj) Object remove(int index) Object get(int index) boolean isEmpty() int size() Copyright © 2017 Pearson Education, Inc.

The ArrayList Class The type of object stored in the list is established when the ArrayList object is created: ArrayList<String> names = new ArrayList<String>(); ArrayList<Book> list = new ArrayList<Book>(); This makes use of Java generics, which provide additional type checking at compile time An ArrayList object cannot store primitive types, but that's what wrapper classes are for See Beatles.java Copyright © 2017 Pearson Education, Inc.

//******************************************************************** // Beatles.java Author: Lewis/Loftus // // Demonstrates the use of a ArrayList object. import java.util.ArrayList; public class Beatles { //----------------------------------------------------------------- // Stores and modifies a list of band members. public static void main(String[] args) ArrayList<String> band = new ArrayList<String>(); band.add("Paul"); band.add("Pete"); band.add("John"); band.add("George"); continue Copyright © 2017 Pearson Education, Inc.

System.out.println(band); int location = band.indexOf("Pete"); continue System.out.println(band); int location = band.indexOf("Pete"); band.remove(location); System.out.println("At index 1: " + band.get(1)); band.add(2, "Ringo"); System.out.println("Size of the band: " + band.size()); int index = 0; while (index < band.size()) { System.out.println(band.get(index)); index++; } Copyright © 2017 Pearson Education, Inc.

Output [Paul, Pete, John, George] [Paul, John, George] At index 1: John Size of the band: 4 Paul John Ringo George continue System.out.println(band); int location = band.indexOf("Pete"); band.remove(location); System.out.println("At index 1: " + band.get(1)); band.add(2, "Ringo"); System.out.println("Size of the band: " + band.size()); int index = 0; while (index < band.size()) { System.out.println(band.get(index)); index++; } Copyright © 2017 Pearson Education, Inc.