TreeMap (SortedMap m)

public TreeMap(SortedMap<K, ? extends V> m)

Constructs a new tree map containing the same mappings and using the same ordering as the specified sorted map. 

import java.util.*;

class TreeMapConstructor4{
 public static void main(String args[]){
  TreeMap<Integer, String> myMap1;
  TreeMap<Integer, String> myMap2;
  SortedMap<Integer, String> subMap;
  
  myMap2 = new TreeMap<> ();
  
  /* Add Elements to myMap2 */
  myMap2.put(10, "c");
  myMap2.put(1, "a");
  myMap2.put(15, "d");
  myMap2.put(5, "b");
  myMap2.put(99, "e");
  
  subMap = myMap2.subMap(5, 20);
  
  System.out.println("Elements in myMap2 are");
  System.out.println(myMap2);
  
  System.out.println("Elements in subMap are");
  System.out.println(subMap);
  
  myMap1 = new TreeMap<> (subMap);
  
  System.out.println("Elements in myMap1 are");
  System.out.println(myMap1);
  
 }
}

Output

Elements in myMap2 are
{1=a, 5=b, 10=c, 15=d, 99=e}
Elements in subMap are
{5=b, 10=c, 15=d}
Elements in myMap1 are
{5=b, 10=c, 15=d}

1. Throws NullPointerException if the specified map is null

import java.util.*;

class TreeMapConstructor4NullPointer{
 public static void main(String args[]){
  TreeMap<Integer, String> myMap1;
  SortedMap<Integer, String> subMap;
  
  subMap = null;
  
  myMap1 = new TreeMap<> (subMap);
  
  System.out.println("Elements in myMap1 are");
  System.out.println(myMap1);
 }
}

Output

Exception in thread "main" java.lang.NullPointerException
        at java.util.TreeMap.<init>(TreeMap.java:198)
        at TreeMapConstructor4NullPointer.main(TreeMapConstructor4NullPointer.ja
va:10)

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