YouTipJava Hashmap Put
# Java HashMap put() Method
[ Java HashMap](#)
The put() method inserts the specified key/value pair into the HashMap.
The syntax for the put() method is:
hashmap.put(K key, V value)
**Note:** hashmap is an object of the HashMap class.
**Parameter Description:**
* key - The key
* value - The value
### Return Value
If the value corresponding to the inserted key already exists, a value replacement operation is performed, and the old value is returned. If it does not exist, an insertion is performed, and null is returned.
### Example
The following example demonstrates the use of the put() method (when the value corresponding to the key does not exist):
## Example
import java.util.HashMap;
class Main {
public static void main(String[] args){
// Create a HashMap
HashMap sites =new HashMap();
// Add some elements to the HashMap
sites.put(1, "Google");
sites.put(2, "");
sites.put(3, "Taobao");
System.out.println("HashMap: "+ sites);
}
}
The output of the above program is:
HashMap: {1=Google, 2=, 3=Taobao}
In the above example, we created a HashMap named `sites`. The code later used the `put()` method to insert this key/value mapping into the HashMap.
Insert multiple key/value pairs using the [Java HashMap putAll() method](#).
**Note:** Each item is inserted randomly into the HashMap.
Example where the value corresponding to the key already exists:
## Example
import java.util.HashMap;
class Main {
public static void main(String[] args){
// Create a HashMap
HashMap sites =new HashMap();
// Add some elements to the HashMap
sites.put(1, "Google");
sites.put(2, "");
sites.put(3, "Taobao");
System.out.println("HashMap: "+ sites);
// Add a duplicate key element
String value = sites.put(1, "Weibo");
System.out.println("Modified HashMap: "+ sites);
// View the replaced value
System.out.println("Replaced value: "+ value);
}
}
The output of the above program is:
Modified HashMap: {1=Weibo, 2=, 3=Taobao}Replaced value: Google
[ Java HashMap](#)