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Map putAll() Method in Java with Examples

Last Updated : 02 Jan, 2019
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This method is used to copy all of the mappings from the specified map to this map. Syntax: 
void putAll(Map m)
Parameters: This method has the only argument map m, which contains key-value mappings to be copied to given map. Returns: This method returns previous value associated with the key if present, else return -1. Below programs show the implementation of int putAll() method. Program 1: Java 
// Java code to show the implementation of // putAll method in Map interface import java.util.*; public class GfG {  // Driver code  public static void main(String[] args)  {  // Initializing a Map of type HashMap  Map<Integer, String> map = new HashMap<>();  map.put(1, "One");  map.put(3, "Three");  map.put(5, "Five");  map.put(7, "Seven");  map.put(9, "Nine");  System.out.println(map);  Map<Integer, String> mp = new HashMap<>();  mp.put(10, "Ten");  mp.put(30, "Thirty");  mp.put(50, "Fifty");  map.putAll(mp);  System.out.println(map);  } }
Output: 
 {1=One, 3=Three, 5=Five, 7=Seven, 9=Nine} {1=One, 50=Fifty, 3=Three, 5=Five, 7=Seven, 9=Nine, 10=Ten, 30=Thirty}
Program 2: Below is the code to show implementation of put(). Java 
// Java code to show the implementation of // putAll method in Map interface import java.util.*; public class GfG {  // Driver code  public static void main(String[] args)  {  // Initializing a Map of type HashMap  Map<String, String> map = new HashMap<>();  map.put("1", "One");  map.put("3", "Three");  map.put("5", "Five");  map.put("7", "Seven");  map.put("9", "Nine");  System.out.println(map);  Map<String, String> mp = new HashMap<>();  mp.put("10", "Ten");  mp.put("30", "Thirty");  mp.put("50", "Fifty");  map.putAll(mp);  System.out.println(map);  } }
Output: 
 {1=One, 3=Three, 5=Five, 7=Seven, 9=Nine} {1=One, 3=Three, 5=Five, 7=Seven, 9=Nine, 50=Fifty, 30=Thirty, 10=Ten}
Reference: Oracle Docs

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