HashMap putAll() Method in Java

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The putAll() method of HashMap copies all the entries of the specified map into this map. It throws NullPointerException if the specified map is null, or if this map does not permit null keys or values, and the specified map contains null keys or values.


void putAll(Map<K,V> map)


The map we want to copy


import java.util.HashMap;
import java.util.Map;

public class HashMapPutAllExample {

	public static void main(String[] args) {

		Map<Integer, String> alphabates = new HashMap<>();
		Map<Integer, String> vowels = new HashMap<>();
		alphabates.put(21, "G");
		alphabates.put(19, "F");
		alphabates.put(13, "C");
		alphabates.put(24, "D");

		vowels.put(1, "A");
		vowels.put(2, "E");
		vowels.put(3, "I");
		vowels.put(4, "O");
		vowels.put(5, "U");
		System.out.println("Elements of alaphabates map: " + alphabates);
		System.out.println("Elements of vowels map: " + vowels);
		System.out.println("Elements of alphabates after adding all elements of vowels: " + alphabates);



Elements of alaphabates map: {19=F, 21=G, 24=D, 13=C}
Elements of vowels map: {1=A, 2=E, 3=I, 4=O, 5=U}
Elements of alphabates after adding all elements of vowels: {1=A, 2=E, 19=F, 3=I, 4=O, 21=G, 5=U, 24=D, 13=C}
Categories: Java