Java - How to Get a Sublist of TreeMap

  In the example below we will see how to get from a TreeMap a new sub-TreeMap sorted using the subMap() of the TreeMap.

subMap(K fromKey, K toKey)

Example:

import java.util.*; 

class TreeMapSub {
 
 public static void main(String args[]) {
 
 TreeMap treemap = new TreeMap(); 

 // elements
 treemap.put("a", "e4"); 
 treemap.put("b", "e5"); 
 treemap.put("c", "e1"); 
 treemap.put("d", "e3"); 
 treemap.put("e", "e2"); 
 
 System.out.println("Before:"); 
 
 /* browse the unsorted TreeMap with Iterator */
 
 Set set = treemap.entrySet(); 
 Iterator i = set.iterator(); 
 // Show elements
 while(i.hasNext()) {
 Map.Entry entry = (Map.Entry)i.next(); 
 System.out.print(entry.getKey() + " : "); 
 System.out.println(entry.getValue()); 
 }
 
 System.out.println("After:"); 
 
 // call the subMap()
 SortedMap subM = treemap.subMap("a","d"); 
 
 /* browse the submap with Iterator */
 
 set = subM.entrySet(); 
 i = set.iterator(); 
 // Show elements
 while(i.hasNext()) {
 Map.Entry entry = (Map.Entry)i.next(); 
 System.out.print(entry.getKey() + " : "); 
 System.out.println(entry.getValue()); 
 }
 
 }
}

Runtime

Front:
a: e4
b: e5
c: e1
d:  e3
e: e2
After:
a: e4
b: e5
c: e1

References
java.util.TreeMap.subMap() Method