Java Iterator Interface

In this tutorial, we will learn about the Java Iterator Interface with the help of an example.

The Iterator interface of the Java collections system allows us to get to components of an assortment. It has a subinterface ListIterator.

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All the Java collections incorporate an iterator() strategy. This strategy returns an occasion of iterator used to emphasize over components of collections.

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Methods of Iterator

The Iterator interface gives 4 methods that can be used to perform different procedure on components of collections.

• hasNext() – returns true if there exists an element in the collection
• next() – returns the next element of the collection
• remove() – removes the last element returned by the next()
• forEachRemaining() – performs the specified action for each remaining element of the collection

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Example: Implementation of Iterator

In the example beneath, we have actualized the hasNext(), next(), eliminate() and forEachRemining() methods for the Iterator interface in an exhibit list.

import java.util.ArrayList;
import java.util.Iterator;

class Main {
    public static void main(String[] args) {
        // Creating an ArrayList
        ArrayList<Integer> numbers = new ArrayList<>();
        numbers.add(1);
        numbers.add(3);
        numbers.add(2);
        System.out.println("ArrayList: " + numbers);

        // Creating an instance of Iterator
        Iterator<Integer> iterate = numbers.iterator();

        // Using the next() method
        int number = iterate.next();
        System.out.println("Accessed Element: " + number);

        // Using the remove() method
        iterate.remove();
        System.out.println("Removed Element: " + number);

        System.out.print("Updated ArrayList: ");

        // Using the hasNext() method
        while(iterate.hasNext()) {
            // Using the forEachRemaining() method
            iterate.forEachRemaining((value) -> System.out.print(value + ", "));
        }
    }
}

Output

ArrayList: [1, 3, 2]
Acessed Element: 1
Removed Element: 1
Updated ArrayList: 3, 2,

In the above example, notice the statement:

iterate.forEachRemaining((value) -> System.put.print(value + ", "));

Here, we have passed the lambda expression as an argument of the forEachRemaining() method.

Now the method will print all the remaining elements of the array list.

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