Collection Framework Example

In the following example, we have used the TreeMap method, which stores its elements in a tree and orders its elements based on their values. Here in the example we have used the key of the element to show the values of the element. To retrieve the keys and values use keySet() and values() method respectively. 
This program shows the data elements left after removing the particular element by specifying its key. Using the Iterator interface methods, we can traverse a collection from start to finish and safely remove elements from the underlying Collection.
 Here is the code of program:

import java.util.*; public class TreeMapExample{   public static void main(String[] args) {     System.out.println("Tree Map Example!\n");     TreeMap <Integer, String>tMap = new TreeMap<Integer, String>();     //Addding data to a tree map     tMap.put(1, "Sunday");     tMap.put(2, "Monday");     tMap.put(3, "Tuesday");     tMap.put(4, "Wednesday");     tMap.put(5, "Thursday");     tMap.put(6, "Friday");     tMap.put(7, "Saturday");     //Rerieving all keys     System.out.println("Keys of tree map: " + tMap.keySet());     //Rerieving all values     System.out.println("Values of tree map: " + tMap.values());     //Rerieving the value from key with key number 5     System.out.println("Key: 5 value: " + tMap.get(5)+ "\n");     //Rerieving the First key and its value     System.out.println("First key: " + tMap.firstKey() + " Value: "                                      + tMap.get(tMap.firstKey()) + "\n");     //Rerieving the Last key and value     System.out.println("Last key: " + tMap.lastKey() + " Value: "                                         + tMap.get(tMap.lastKey()) + "\n");     //Removing the first key and value     System.out.println("Removing first data: " + tMap.remove(tMap.firstKey()));     System.out.println("Now the tree map Keys: " + tMap.keySet());     System.out.println("Now the tree map contain: " + tMap.values() + "\n");     //Removing the last key and value     System.out.println("Removing last data: " + tMap.remove(tMap.lastKey()));     System.out.println("Now the tree map Keys: " + tMap.keySet());     System.out.println("Now the tree map contain: " + tMap.values());   } }