Java HashMap replaceAll() Method

The replaceAll() method replaces all mappings in the hashMap with the results of the given function.

The syntax for the replaceAll() method is:

hashmap.replaceAll(BiFunction&lt;K, V> function)

Note: hashmap is an object of the HashMap class.

Parameter Description:

function - The function to be executed.

Return Value

This method does not return any value; it only replaces all values in the HashMap.

Example

The following example demonstrates the use of the replaceAll() method:

import java.util.HashMap;

class Main {
    public static void main(String[] args) {
        // Create a HashMap
        HashMap&lt;Integer, String> sites = new HashMap<>();

        // Add some elements to the HashMap
        sites.put(1, "Google");
        sites.put(2, "tutorialpro");
        sites.put(3, "Taobao");
        System.out.println("sites HashMap: " + sites);

        // Change all values to uppercase
        sites.replaceAll((key, value) -> value.toUpperCase());
        System.out.println("Updated HashMap: " + sites);
    }
}

Output:

sites HashMap: {1=Google, 2=tutorialpro, 3=Taobao}
Updated HashMap: {1=GOOGLE, 2=TUTORIALPRO, 3=TAOBAO}

(key, value) -> value.toUpperCase() is an anonymous function lambda expression. It converts all values in the HashMap to uppercase and returns them. For more information, visit Java Lambda Expressions.

Replace all values with the square of the keys:

import java.util.HashMap;

class Main {
    public static void main(String[] args) {
        // Create a HashMap
        HashMap&lt;Integer, Integer> numbers = new HashMap<>();

        // Add mappings to the HashMap
        numbers.put(5, 0);
        numbers.put(8, 1);
        numbers.put(9, 2);
        System.out.println("HashMap: " + numbers);

        // Replace all values with the square of the keys
        numbers.replaceAll((key, value) -> key * key);
        System.out.println("Updated HashMap: " + numbers);
    }
}

Output:

HashMap: {5=0, 8=1, 9=2}
Updated HashMap: {5=25, 8=64, 9=81}

Java HashMap

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