How to use an ArrayList - java.util.ArrayList

JavaPF · #1 (**permalink**) 15-05-2009, 01:34 PM

A lot of people ask me how to use an ArrayList and also ask what is the advantage of an ArrayList over a standard Array.

If the data has a known number of elements or small fixed size upper bound, arrays are often the best choice. However, many data storage problems are not that simple. The main advantage to an ArrayList is that it automatically expands as data is added. A disadvantage is that an ArrayList cannot work with primitive types.

Here is a quick example to show you how to add, print, and remove data from an ArrayList:

Java Code:

// Import ArrayList
import java.util.ArrayList;

public class ArrayListExample {

    /**
     * JavaProgrammingForums.com
     */
    public static void main(String[] args) {

        // Construct a new empty ArrayList for type String
        ArrayList<String> al = new ArrayList<String>();

        // Fill ArrayList (index, String)
        al.add(0, "Java");
        al.add(1, "Programming");
        al.add(2, "Forums");
        al.add(3, ".com");
                
        // Convert ArrayList to Object array
        Object[] elements = al.toArray();
        
        // Print Object content
        for (int a = 0; a < elements.length; a++) {
            System.out.println(elements[a]);
        }
        
        // Remove item from ArrayList
        al.remove(3);

        // Clear entire ArrayList
        al.clear();
    }

}

Fendaril · #2 (**permalink**) 17-05-2009, 06:12 PM

You forgot to add that ArrayLists cannot work with primitive types.

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The Following User Says Thank You to Fendaril For This Useful Post:
JavaPF (17-05-2009)