cursors in java

What are cursors in java?

• If we want to retrieve objects one by one from the collection then we should go for Cursor. There are 3 types of cursors available in java.

1) Enumeration

2) Iterator

3) ListIterator

Enumeration:

• We can use enumeration to get objects one by one from the Legacy collection object.

• Enumeration is an Interface

• We can create enumeration objects by using elements() method of vector class. [Learn about vector class]

//public enumeration elements() -- method available in vector class
//Enumeration e= v.elements();
//public boolean hasMoreElements() -- method available in Enumeration interface
//public object nextElement() -- method available in Enumeration interface

Demo program on Enumeration:

public class CursorsDemo {
    public static void main(String[] args) {
        Vector v = new Vector();
        for (int i = 0; i < 10; i++) {
            v.addElement(i);
        }
        System.out.println(v); //[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]    
    Enumeration e = v.elements();
        while (e.hasMoreElements()) {
            Integer i = (Integer) e.nextElement();
            if ((i % 2) != 0)
                System.out.println(i); //[1 3 5 7 9]        
}
        System.out.println(v);//[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]    }
}

Output:

cursors in java

Limitations of Enumeration:

• We can apply enumeration concept only for legacy classes and it is not a universal cursor
• By using enumeration we can get only read access and we can't perform remove operation

To overcome above limitations we should go for Iterator .

Please comment below to feedback or ask questions.