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Map put() Method in Java with Examples

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The Map put() method associates the specified value with the specified key in the map. The map put() method is used to insert new key-value pairs inside a map in Java.

If the map already contains the mapping for the specified key, the old value is replaced by the new specified value.

Example:

Java

// Java Program to demonstrate the
// Usage of put() method in Map interface
import java.util.HashMap;
import java.util.Map;
 
// Driver Class
public class MapPutExample {
      // Main Function
    public static void main(String[] args) {
        // Create a HashMap instance
        Map<String, Integer> map = new HashMap<>();
 
        // Add key-value pairs to the map
        map.put("One", 1);
        map.put("Two", 2);
 
        // Display the map after adding elements
        System.out.println("Map after adding elements: " + map);
 
        // Replace the value associated with key
        // 'Two' and store the previous value
        Integer oldValue = map.put("Two", 22);
 
        // Display the previous value associated with key 'Two'
        System.out.println("Previous value for key 'Two': " + oldValue);
 
        // Display the map after updating the value for key 'Two'
        System.out.println("Map after updating 'Two': " + map);
    }
}

                    

Output:

Map after adding elements: {One=1, Two=2}
Previous value for key 'Two': 2
Map after updating 'Two': {One=1, Two=22}

Syntax

V put(K key, V value)

Parameters

This method has two arguments, key and value where the key is the left argument and the value is the corresponding value of the key in the map.

Returns

Returns the previous value associated with the key if present, else returns a null value

Exceptions

  • NullPointerException– When the specified key is null
  • ClassCastException- When the type of key-value pair is incompatible with the map.

Map put() Method Examples

Let’s see some examples of how to use the map put() method:

Example 1

How to insert/add elements in a map using the map put() method:

Java

// Java code to show the implementation of
// put 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);
    }
}

                    

Output
{1=One, 3=Three, 5=Five, 7=Seven, 9=Nine}

Example 2

Below is the code to show the implementation of put(). 

Java

// Java code to show the implementation of
// put 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);
    }
}

                    

Output
{1=One, 3=Three, 5=Five, 7=Seven, 9=Nine}

Read More Map Methods

Whether you are a beginner starting Java programming or an experienced looking to brush up on your Java skills, this tutorial will provide you with a deep understanding of the map put function and its uses in Java.

The map put method in Java is a fundamental function for map manipulation. With this guide, you can easily add new key-value pairs using the map put function.



Last Updated : 16 Feb, 2024
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