Java HashMap putAll() Method
Java HashMapThe putAll() method inserts all the specified key/value pairs into the HashMap.
The syntax of the putAll() method is:
hashmap.putAll(Map m)
Note:hashmap is an object of the HashMap class.
Parameter Details:
- m - contains the mappings to be inserted into the HashMap
Return Value
It does not return any value.
Example
The following example demonstrates the use of the putAll() method:
Example
import java.util.HashMap;
class Main {
public static void main(String[] args) {
// Create a HashMap
HashMap<Integer, String> sites = new HashMap<>();
// Add some elements to the HashMap
sites.put(1, "Google");
sites.put(2, "Example");
sites.put(3, "Taobao");
System.out.println("sites HashMap: " + sites);
// Create another HashMap
HashMap<Integer, String> sites2 = new HashMap<>();
sites2.put(1, "Weibo"); // Existing values will be replaced
sites2.put(4, "Wiki");
// Add all mappings from sites to sites2
sites2.putAll(sites);
System.out.println("sites2 HashMap: " + sites2);
}
}
class Main {
public static void main(String[] args) {
// Create a HashMap
HashMap<Integer, String> sites = new HashMap<>();
// Add some elements to the HashMap
sites.put(1, "Google");
sites.put(2, "Example");
sites.put(3, "Taobao");
System.out.println("sites HashMap: " + sites);
// Create another HashMap
HashMap<Integer, String> sites2 = new HashMap<>();
sites2.put(1, "Weibo"); // Existing values will be replaced
sites2.put(4, "Wiki");
// Add all mappings from sites to sites2
sites2.putAll(sites);
System.out.println("sites2 HashMap: " + sites2);
}
}
Executing the above program produces the following output:
sites HashMap: {1=Google, 2=Example, 3=Taobao}
sites2 HashMap: {1=Google, 2=Example, 3=Taobao, 4=Wiki}
In the above example, we created two HashMaps: sites and site2. Later in the code, the putAll() method is used to insert sites' key/value pairs into site2. Since key 1 already exists in site2, the corresponding value from sites will replace the corresponding value in site2.
Inserting a single key/valueJava HashMap put() Method。
Other Extensions