How to Remove a Key-Value Pair from a Map in Java - Step by Step Examples

How to Remove a Key-Value Pair from a Map in Java ?

Answer

To remove a key-value pair from a map in Java, you can use the remove method. This method allows you to remove the key-value pair associated with the specified key.

✐ Examples

1 Removing a Key-Value Pair Using remove Method

We can remove a key-value pair from a map in Java using the remove method, which removes the key-value pair associated with the specified key.

For example,

We start by importing the java.util.HashMap package, which provides the HashMap class needed to create and manipulate the map.
We declare and initialize a map named myMap with some key-value pairs. In this example, the map has integer keys and string values.
We use the remove method to remove the key-value pair associated with the key 2. The remove method removes the key-value pair from the map and returns the value associated with the removed key.
We print the contents of the map to the console using a for loop and System.out.println to verify that the key-value pair has been removed.

Java Program

import java.util.HashMap;
import java.util.Map;

public class Main {
    public static void main(String[] args) {
        // Declare and initialize a map
        Map<Integer, String> myMap = new HashMap<>();
        myMap.put(1, "one");
        myMap.put(2, "two");
        myMap.put(3, "three");

        // Remove a key-value pair using remove method
        myMap.remove(2);

        // Print the contents of the map
        for (Map.Entry<Integer, String> entry : myMap.entrySet()) {
            System.out.println(entry.getKey() + ": " + entry.getValue());
        }
    }
}

Output

1: one
3: three

2 Handling Key Not Found Using remove Method

We can handle the case where a key is not found in a map in Java using the remove method, which returns null if the key is not present.

For example,

We start by importing the java.util.HashMap package, which provides the HashMap class needed to create and manipulate the map.
We declare and initialize a map named myMap with some key-value pairs. In this example, the map has integer keys and string values.
We use the remove method to attempt to remove the key-value pair associated with the key 4. The remove method returns null if the key is not found.
We print the contents of the map to the console using a for loop and System.out.println to verify that the map is unchanged.

Java Program

import java.util.HashMap;
import java.util.Map;

public class Main {
    public static void main(String[] args) {
        // Declare and initialize a map
        Map<Integer, String> myMap = new HashMap<>();
        myMap.put(1, "one");
        myMap.put(2, "two");
        myMap.put(3, "three");

        // Attempt to remove a non-existent key-value pair using remove method
        myMap.remove(4);

        // Print the contents of the map
        for (Map.Entry<Integer, String> entry : myMap.entrySet()) {
            System.out.println(entry.getKey() + ": " + entry.getValue());
        }
    }
}

Output

1: one
2: two
3: three

3 Removing Multiple Key-Value Pairs Using remove Method

We can remove multiple key-value pairs from a map in Java using the remove method, which removes the key-value pairs associated with the specified keys.

For example,

We start by importing the java.util.HashMap package, which provides the HashMap class needed to create and manipulate the map.
We declare and initialize a map named myMap with some key-value pairs. In this example, the map has integer keys and string values.
We use the remove method to remove the key-value pairs associated with the keys 1 and 3. The remove method removes the key-value pairs from the map and returns the value associated with the removed keys.
We print the contents of the map to the console using a for loop and System.out.println to verify that the key-value pairs have been removed.

Java Program

import java.util.HashMap;
import java.util.Map;

public class Main {
    public static void main(String[] args) {
        // Declare and initialize a map
        Map<Integer, String> myMap = new HashMap<>();
        myMap.put(1, "one");
        myMap.put(2, "two");
        myMap.put(3, "three");

        // Remove multiple key-value pairs using remove method
        myMap.remove(1);
        myMap.remove(3);

        // Print the contents of the map
        for (Map.Entry<Integer, String> entry : myMap.entrySet()) {
            System.out.println(entry.getKey() + ": " + entry.getValue());
        }
    }
}

Output

2: two

Summary

In this tutorial, we learned How to Remove a Key-Value Pair from a Map in Java language with well detailed examples.

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How to Remove a Key-Value Pair from a Map in Java - Step by Step Examples