In Java how to transform a Map<K,V> to another Map<K,V> using a lambda?

In Java how to transform a Map<K,V> to another Map<K,V> using a lambda?

You can transform a Map<K, V> to another Map<K, V> using a lambda expression in Java by iterating over the entries of the original map and applying a transformation function to each entry. You can achieve this using the Stream API and the Collectors.toMap collector. Here's how you can do it:

Suppose you have a Map<String, Integer> and you want to create another Map<String, String> where each value is converted to a string representation. You can use a lambda expression for this transformation:

import java.util.HashMap; import java.util.Map; import java.util.stream.Collectors; public class MapTransformationExample { public static void main(String[] args) { Map<String, Integer> originalMap = new HashMap<>(); originalMap.put("one", 1); originalMap.put("two", 2); originalMap.put("three", 3); // Transform the original map to a new map Map<String, String> transformedMap = originalMap.entrySet() .stream() .collect(Collectors.toMap( Map.Entry::getKey, // Key remains the same entry -> String.valueOf(entry.getValue()) // Value transformation to String )); System.out.println("Original Map: " + originalMap); System.out.println("Transformed Map: " + transformedMap); } }

In this example:

  1. We have an original Map<String, Integer> named originalMap.
  2. We use the entrySet() method to get a set of map entries.
  3. We create a stream of these entries using .stream().
  4. We use Collectors.toMap to collect the entries into a new map, where the lambda expression specifies how to map the keys (unchanged) and how to transform the values (convert to a string using String.valueOf()).

After running this code, you'll get a new Map<String, String> where the values are transformed to strings while keeping the original keys intact.

More Tags

conda android-studio-3.1 rake python-c-api network-printers pika razorengine call default-constructor oracle-apex-5.1

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