TreeMap putAll() method in java

Let’s learn TreeMap putAll() method in java.

TreeMap putAll() method in java

putAll() method of TreeMap class copies all of the mappings from the specified map to this map.

These mappings replace any mappings that this map had for any of the keys currently in the specified map.


public void putAll(Map<? extends K,? extends V> map)


map mappings to be stored in this map.


ClassCastException – if the class of a key or value in the specified map prevents it from being stored in this map.

NullPointerException – if the specified map is null or the specified map contains a null key and this map does not permit null keys.

Also read – TreeMap in java

Now let’s see example on TreeMap putAll() method.

import java.util.TreeMap;
public class TreeMapPutAllMethodExample
   public static void main(String[] args)
      TreeMap<Integer, String> tm1 = new TreeMap<Integer, String>();
      tm1.put(32, "pineapple");
      tm1.put(51, "watermelon");
      tm1.put(38, "grapes");
      tm1.put(69, "mango");
      tm1.put(58, "apple");
      System.out.println("TreeMap before using putAll() method: " + tm1);
      // create new TreeMap and copy
      TreeMap<Integer, String> tm2 = new TreeMap<Integer, String>();
      System.out.println("TreeMap after using putAll() method: " + tm2);


TreeMap before using putAll() method: {32=pineapple, 38=grapes, 51=watermelon, 58=apple, 69=mango}
TreeMap after using putAll() method: {32=pineapple, 38=grapes, 51=watermelon, 58=apple, 69=mango}