Question
Listed next is a code skeleton for an interface called Enumeration and a class called NameCollection . Enumeration provides an interface to sequentially iterate through some type of collection. In this case, the collection will be the class NameCollection that simply stores a collection of names using an array of strings.
interface Enumeration
{
// Returns true if another element in the collection exists
public boolean hasNext();
// Returns the next element in the collection as an Object
public Object getNext();
}
/**
* NameCollection implements a collection of names using
* a simple array.
*/
class NameCollection
{
String[] names;
/**
* The list of names is initialized from outside
* and passed in as an array of strings
*/
NameCollection(String[] names)
{
this.names = names;
}
/**
* getEnumeration should return an instance of a class that
* implements the Enumeration interface where hasNext() and getNext()
* correspond to data stored within the names array.
*/
Enumeration getEnumeration ()
{
// Complete code here using an inner class
}
}
Complete the method getEnumeration() so that it returns an anonymous inner class that corresponds to the Enumeration interface for the names array in NamesCollection. Then write a main method that creates a NamesCollection object with a sample array of strings, retrieves the Enumeration for this class via getEnumeration(), and then iterates through the enumeration outputting each name using the getNext() method.
Answer
PROGRAM CODE:
interface Enumeration
{
// Returns true if another element in the collection exists
boolean hasNext();
// Returns the next element in the collection as an Object
Object getNext();
}
/**
* NameCollection implements a collection of names using a simple array.
*/
class NameCollection
{
String[] names;
/**
* The list of names is initialized from outside and passed in as an array of strings
*/
NameCollection(String[] names)
{
this.names = names;
}
/**
* getEnumeration should return an instance of a class that implements the Enumeration interface
* where hasNext() and getNext() correspond to data stored within the names array.
*/
Enumeration getEnumeration()
{
// Return an instance of an anonymous inner class that implements
// the Enumeration interface
return new Enumeration()
{
private int index = 0;
@Override
public boolean hasNext()
{
return index < names.length;
}
@Override
public Object getNext()
{
if (hasNext())
{
return names[index++];
}
return null;
}
};
}
}
public class Main
{
public static void main(String[] args)
{
// Sample array of names
String[] namesArray = {"Alice", "Bob", "Charlie", "David"};
// Create a NameCollection object with the sample array
NameCollection nameCollection = new NameCollection(namesArray);
// Retrieve the Enumeration for this class via getEnumeration()
Enumeration enumeration = nameCollection.getEnumeration();
// Iterate through the enumeration and output each name using the getNext() method
while (enumeration.hasNext()) {
System.out.println(enumeration.getNext());
}
}
}
OUTPUT:
Alice
Bob
Charlie
David