How to Swap Keys and Values in a Map in Java - Step by Step Examples

We can swap keys and values in a map of integers in Java by iterating over the original map and inserting each key-value pair into a new map with the value as the key and the key as the value.

For example,

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

public class SwapMap {
    public static void main(String[] args) {
        // Declare and initialize a map of integers
        Map<Integer, Integer> originalMap = new HashMap<>();
        originalMap.put(1, 10);
        originalMap.put(2, 20);
        originalMap.put(3, 30);
        originalMap.put(4, 40);
        originalMap.put(5, 50);

        // Declare an empty map to store the swapped key-value pairs
        Map<Integer, Integer> swappedMap = new HashMap<>();

        // Iterate over the original map and insert each key-value pair into the new map with the value as the key and the key as the value
        for (Map.Entry<Integer, Integer> entry : originalMap.entrySet()) {
            swappedMap.put(entry.getValue(), entry.getKey());
        }

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

Swapped map of integers:
10: 1
20: 2
30: 3
40: 4
50: 5

We can swap keys and values in a map of strings in Java by iterating over the original map and inserting each key-value pair into a new map with the value as the key and the key as the value.

For example,

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

public class SwapMap {
    public static void main(String[] args) {
        // Declare and initialize a map of strings
        Map<String, String> originalMap = new HashMap<>();
        originalMap.put("one", "uno");
        originalMap.put("two", "dos");
        originalMap.put("three", "tres");
        originalMap.put("four", "cuatro");
        originalMap.put("five", "cinco");

        // Declare an empty map to store the swapped key-value pairs
        Map<String, String> swappedMap = new HashMap<>();

        // Iterate over the original map and insert each key-value pair into the new map with the value as the key and the key as the value
        for (Map.Entry<String, String> entry : originalMap.entrySet()) {
            swappedMap.put(entry.getValue(), entry.getKey());
        }

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

Swapped map of strings:
uno: one
dos: two
tres: three
cuatro: four
cinco: five

We can swap keys and values in a map with mixed key and value types in Java by iterating over the original map and inserting each key-value pair into a new map with the value as the key and the key as the value. This example demonstrates swapping keys of type int with values of type String.

For example,

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

public class SwapMap {
    public static void main(String[] args) {
        // Declare and initialize a map with mixed types
        Map<Integer, String> originalMap = new HashMap<>();
        originalMap.put(1, "one");
        originalMap.put(2, "two");
        originalMap.put(3, "three");
        originalMap.put(4, "four");
        originalMap.put(5, "five");

        // Declare an empty map to store the swapped key-value pairs
        Map<String, Integer> swappedMap = new HashMap<>();

        // Iterate over the original map and insert each key-value pair into the new map with the value as the key and the key as the value
        for (Map.Entry<Integer, String> entry : originalMap.entrySet()) {
            swappedMap.put(entry.getValue(), entry.getKey());
        }

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

Swapped map of mixed types:
one: 1
two: 2
three: 3
four: 4
five: 5