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About Byron Kiourtzoglou

Byron is a master software engineer working in the IT and Telecom domains. He is an applications developer in a wide variety of applications/services. He is currently acting as the team leader and technical architect for a proprietary service creation and integration platform for both the IT and Telecom industries in addition to a in-house big data real-time analytics solution. He is always fascinated by SOA, middleware services and mobile development. Byron is co-founder and Executive Editor at Java Code Geeks.

TreeMap Iterator example

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() and next() API methods of Iterator.

Let’s take a look at the code snippet that follows:

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.

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