java util AbstractCollection Class

java.util.AbstractCollection Class

AbstractCollection Class in Java

The AbstractCollection class provides a skeletal implementation of the Collection interface. To implement an unmodifiable collection, the programmer needs only to extend AbstractCollection class and provide implementations for the iterator and size methods. (The iterator returned by the iterator method must implement hasNext and next.)

To implement a modifiable collection, the programmer must additionally override AbstractCollection class's add method (which otherwise throws an UnsupportedOperationException), and the iterator returned by the iterator method must additionally implement its remove method.

The programmer should generally provide a void (no argument) and Collection constructor, as per the recommendation in the Collection interface specification.

java.util.AbstractCollection class Example

/*	Java AbstractCollection class Example
	Save with file name AbstractCollectionExample.java	*/
import java.util.AbstractCollection;
import java.util.ArrayList;
public class AbstractCollectionExample
{
	public static void main(String args[])
	{
		// java.util.AbstractCollection DECLARATION
		AbstractCollection al;
		// java.util.AbstractCollection OBJECT CREATION
		al = new ArrayList();
		// ADD AN ELEMENT
		al.add("AbstractCollection Tutorial");
		al.add("Huda Tutorials");
		al.add("Java Tutorials");
		// DUPLICATES ARE ALLOWED
		al.add("Huda Tutorials");
		al.add("C Tutorials");
		al.add("CPP Tutorials");
		// null ALLOWED
		al.add(null);
		// RETURNS COUNT OF ELEMENTS AbstractCollection CONTAINS
		System.out.println("Elements Count : " + al.size());
		// java.util.AbstractCollection OUTPUT
		System.out.println(al);
	}
}