With this example we are going to demonstrate how to obtain a TreeMap Iterator, that is an iterator over the key value pairs of the TreeMap. The TreeMap API provides methods to get an Iterator. In short, to obtain a TreeMap Iterator you should:
- Create a new TreeMap.
- Populate the map with elements, with
put(K key, V value)API method of TreeMap. - Invoke
entrySet()API method of TreeMap. It returns a Collection of the key- value pairs contained in the TreeMap. - Invoke
iterator()API method of Collection to obtain the iterator for the entries. - Iterate through the values with
hasNext()andnext()API methods of Iterator.
Let’s take a look at the code snippet that follows:
01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 | package com.javacodegeeks.snippets.core; import java.util.Collection;import java.util.TreeMap;import java.util.Iterator; public class TreeMapIterator { public static void main(String[] args) { // Create a TreeMap and populate it with elements TreeMap treeMap = new TreeMap(); treeMap.put("key_1","element_1"); treeMap.put("key_2","element_2"); treeMap.put("key_3","element_3"); // Get a set of all the entries (key - value pairs) contained in the TreeMap Collection entrySet = treeMap.entrySet(); // Obtain an Iterator for the entries Set Iterator it = entrySet.iterator(); // Iterate through TreeMap entries System.out.println("TreeMap entries : "); while(it.hasNext())System.out.println(it.next()); }} |
Output:
TreeMap entries :
key_1=element_1
key_2=element_2
key_3=element_3
This was an example of how to obtain a TreeMap Iterator in Java.
