Map put() Method in Java with Examples (original) (raw)

Last Updated : 16 Feb, 2024

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.