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:
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.
