Java HashMap - putAll() Method
The java.util.HashMap.putAll() method is used to copy all of the mappings from the specified map to this map. These mappings will replace any mappings that this map had for any of the keys currently in the specified map.
Syntax
public void putAll(Map<? extends K,? extends V> m)
Here, K and V are the type of key and value respectively maintained by the container.
Parameters
m |
Specify mappings to be stored in this map. |
Return Value
void type.
Exception
Throws NullPointerException, if the specified map is null.
Example:
In the example below, the java.util.HashMap.putAll() method is used to copy all of the mappings from the Map2 to Map1.
import java.util.*;
public class MyClass {
public static void main(String[] args) {
//creating hash maps
HashMap<Integer, String> Map1 = new HashMap<Integer, String>();
HashMap<Integer, String> Map2 = new HashMap<Integer, String>();
//populating Map2
Map2.put(101, "John");
Map2.put(102, "Marry");
Map2.put(103, "Kim");
Map2.put(104, "Jo");
//printing Map1
System.out.println("Before putAll, Map1 contains: " + Map1);
//copy mapping from Map2 into Map1
Map1.putAll(Map2);
//printing Map1
System.out.println("After putAll, Map1 contains: " + Map1);
}
}
The output of the above code will be:
Before putAll, Map1 contains: {}
After putAll, Map1 contains: {104=Jo, 101=John, 102=Marry, 103=Kim}
❮ Java.util - HashMap
