How to Convert an Array of Key-Value Pairs to a Map in Java - Step by Step Examples

How to Convert an Array of Key-Value Pairs to a Map in Java ?

Answer

To convert an array of key-value pairs to a map in Java, you can iterate over the array and insert each key-value pair into the map. This method allows you to create a map from a collection of key-value pairs stored in an array.

✐ Examples

1 Converting an Array of Pairs to a Map

We can convert an array of key-value pairs to a map in Java by iterating over the array and adding each key-value pair to the map.

For example,

We start by importing the java.util.HashMap and java.util.Map classes, which provide the necessary functions and data structures for working with maps.
We declare and initialize an array of key-value pairs named pairs. In this example, the pairs are represented as arrays with two elements: a key and a value.
We declare an empty map named myMap to store the key-value pairs.
We iterate over the array using a for loop and add each pair to the map.
We print the resulting map to the console using the System.out.println function to verify the conversion.

Java Program

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

public class Main {
    public static void main(String[] args) {
        // Declare and initialize an array of key-value pairs
        int[][] pairs = {
            {1, 10},
            {2, 20},
            {3, 30},
            {4, 40},
            {5, 50}
        };

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

        // Iterate over the array and add each pair to the map
        for (int[] pair : pairs) {
            myMap.put(pair[0], pair[1]);
        }

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

Output

Map from array of pairs:
1: 10
2: 20
3: 30
4: 40
5: 50

2 Converting an Array of Map Entries to a Map

We can convert an array of map entries to a map in Java by iterating over the array and adding each entry to the map.

For example,

We start by importing the java.util.HashMap, java.util.Map, and java.util.AbstractMap.SimpleEntry classes, which provide the necessary functions and data structures for working with maps and map entries.
We declare and initialize an array of map entries named entries with some key-value pairs.
We declare an empty map named myMap to store the key-value pairs.
We iterate over the array using a for loop and add each entry to the map.
We print the resulting map to the console using the System.out.println function to verify the conversion.

Java Program

import java.util.HashMap;
import java.util.Map;
import java.util.AbstractMap.SimpleEntry;

public class Main {
    public static void main(String[] args) {
        // Declare and initialize an array of map entries
        SimpleEntry<Integer, Integer>[] entries = new SimpleEntry[] {
            new SimpleEntry<>(1, 10),
            new SimpleEntry<>(2, 20),
            new SimpleEntry<>(3, 30),
            new SimpleEntry<>(4, 40),
            new SimpleEntry<>(5, 50)
        };

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

        // Iterate over the array and add each entry to the map
        for (SimpleEntry<Integer, Integer> entry : entries) {
            myMap.put(entry.getKey(), entry.getValue());
        }

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

Output

Map from array of entries:
1: 10
2: 20
3: 30
4: 40
5: 50

3 Converting a List of Key-Value Pairs to a Map

We can convert a list of key-value pairs to a map in Java by iterating over the list and adding each key-value pair to the map.

For example,

We start by importing the java.util.HashMap, java.util.Map, and java.util.List classes, which provide the necessary functions and data structures for working with maps and lists.
We declare and initialize a list of key-value pairs named pairs with some key-value pairs. In this example, the pairs are represented as arrays with two elements: a key and a value.
We declare an empty map named myMap to store the key-value pairs.
We iterate over the list using a for loop and add each pair to the map.
We print the resulting map to the console using the System.out.println function to verify the conversion.

Java Program

import java.util.HashMap;
import java.util.Map;
import java.util.List;
import java.util.Arrays;

public class Main {
    public static void main(String[] args) {
        // Declare and initialize a list of key-value pairs
        List<int[]> pairs = Arrays.asList(
            new int[]{1, 10},
            new int[]{2, 20},
            new int[]{3, 30},
            new int[]{4, 40},
            new int[]{5, 50}
        );

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

        // Iterate over the list and add each pair to the map
        for (int[] pair : pairs) {
            myMap.put(pair[0], pair[1]);
        }

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

Output

Map from list of pairs:
1: 10
2: 20
3: 30
4: 40
5: 50

Summary

In this tutorial, we learned How to Convert an Array of Key-Value Pairs to a Map in Java language with well detailed examples.

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How to Convert an Array of Key-Value Pairs to a Map in Java - Step by Step Examples