Java Program that Shows Use of Collection Interface

// Java Program that Shows Use of Collection Interface
// ArrayList

import java.util.*;

class GFG {
    public static void main(String args[])
    {
        ArrayList<String> list = new ArrayList<String>();
        list.add("Geeks");
        list.add("areyou");
        list.add("working");
        list.add("hard?");

        Iterator itr = list.iterator();
        while (itr.hasNext()) {
            System.out.println(itr.next());
        }
    }
}

// Java Program that Shows Use of Collection Interface
// LinkedList

import java.util.*;

// Class testing java Collection
public class GFG {

    // Main driver method
    public static void main(String args[])
    {
        // Creating a LinkedList
        LinkedList<String> al = new LinkedList<String>();

        // Adding elements to above linked list
        al.add("Geeks");
        al.add("areyou");
        al.add("working");
        al.add("hard?");

        // Iterator
        Iterator<String> itr = al.iterator();

        // Condition check over elements inside using
        // hasNext() method which holds true till there is
        // element inside list
        while (itr.hasNext()) {

            // Printing elements of LinkedList
            System.out.println(itr.next());
        }
    }
}

// Java Program that Shows Use of Collection Interface
// Hash-Map

import java.util.*;
public class GFG {

    // Main driver method
    public static void main(String[] args)
    {
        // Creating a Map
        Map<Integer, String> map = new HashMap<>();

        // Adding elements to map
        map.put(1, "Geeks");
        map.put(2, "are");
        map.put(3, "you");
        map.put(4, "working");

        // Traversing Map
        // Converting to Set so that traversal is accessed
        Set set = map.entrySet();

        // Iterator
        Iterator itr = set.iterator();

        // Condition check over elements inside using
        // hasNext() method which holds true till there is
        // element inside list

        while (itr.hasNext()) {
            // Converting to Map.Entry so that we can get
            // key and value separately

            Map.Entry entry = (Map.Entry)itr.next();

            // Printing elements inside HashMap
            System.out.println(entry.getKey() + " "
                               + entry.getValue());
        }
    }
}

// Java Program that Shows Use of Collection Interface
// Stack

import java.util.*;
public class GFG {

    // Main driver method
    public static void main(String args[])
    {
        // Creating a stack in memory
        Stack<String> stack = new Stack<String>();

        // Adding elements to stack
        stack.push("Geeks");
        stack.push("are");
        stack.push("you");
        stack.push("working");
        stack.push("hard?");

        // pop() returns all elements of stack
        stack.pop();

        //. iterator
        Iterator<String> itr = stack.iterator();

        // Condition check over elements inside using
        // hasNext() method which holds true till there is
        // element inside list
        while (itr.hasNext()) {

            // Print all popped elements
            System.out.println(itr.next());
        }
    }
}