How to Clear All Key-Value Pairs from a Map in Java - Step by Step Examples

How to Clear All Key-Value Pairs from a Map in Java ?

Answer

To clear all key-value pairs from a map in Java, you can use the clear method. This method removes all elements from the map, leaving it empty.

✐ Examples

1 Clearing All Key-Value Pairs Using clear Method

We can clear all key-value pairs from a map in Java using the clear method, which removes all elements from the map.

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 clear method to remove all key-value pairs from the map.
We print the size of the map using the size method to verify that the map is empty.

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");

        // Clear all key-value pairs using clear method
        myMap.clear();

        // Print the size of the map
        System.out.println("Size of the map after clearing: " + myMap.size());
    }
}

Output

Size of the map after clearing: 0

2 Clearing an Already Empty Map

We can use the clear method on an already empty map in Java, and it will still leave the map empty.

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 an empty map named myMap. In this example, the map has integer keys and string values.
We use the clear method to remove all key-value pairs from the map, even though it is already empty.
We print the size of the map using the size method to verify that the map is still empty.

Java Program

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

public class Main {
    public static void main(String[] args) {
        // Declare and initialize an empty map
        Map<Integer, String> myMap = new HashMap<>();

        // Clear the map using clear method
        myMap.clear();

        // Print the size of the map
        System.out.println("Size of the map after clearing: " + myMap.size());
    }
}

Output

Size of the map after clearing: 0

3 Clearing a Map After Inserting Elements

We can insert key-value pairs into a map and then clear all key-value pairs using the clear method.

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 and insert some key-value pairs into it. In this example, the map has integer keys and string values.
We use the clear method to remove all key-value pairs from the map.
We print the size of the map using the size method to verify that the map is empty.

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");

        // Clear all key-value pairs using clear method
        myMap.clear();

        // Print the size of the map
        System.out.println("Size of the map after clearing: " + myMap.size());
    }
}

Output

Size of the map after clearing: 0

Summary

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

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How to Clear All Key-Value Pairs from a Map in Java - Step by Step Examples