Java Creating ConcurrentHashMap from Other Maps

In Java, you can create a ConcurrentHashMap from other maps using the new ConcurrentHashMap(Map m) constructor.

Here is an example of how to create a ConcurrentHashMap from a HashMap:

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

public class Main {
  public static void main(String[] args) {
    // Create a HashMap
    Map<String, Integer> hashMap = new HashMap<>();
    hashMap.put("Apple", 1);
    hashMap.put("Banana", 2);
    hashMap.put("Cherry", 3);

    // Create a ConcurrentHashMap from the HashMap
    ConcurrentHashMap<String, Integer> concurrentHashMap = new ConcurrentHashMap<>(hashMap);

    // Print the ConcurrentHashMap
    System.out.println(concurrentHashMap);  // Output: {Apple=1, Banana=2, Cherry=3}
  }
}

In this example, we create a HashMap and add some key-value pairs to it. We then create a ConcurrentHashMap from the HashMap using the new ConcurrentHashMap(Map m) constructor. This creates a new ConcurrentHashMap with the same key-value pairs as the HashMap.

You can also create a ConcurrentHashMap from other maps, such as a TreeMap or a LinkedHashMap. Here is an example:

import java.util.LinkedHashMap;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

public class Main {
  public static void main(String[] args) {
    // Create a LinkedHashMap
    Map<String, Integer> linkedHashMap = new LinkedHashMap<>();
    linkedHashMap.put("Apple", 1);
    linkedHashMap.put("Banana", 2);
    linkedHashMap.put("Cherry", 3);

    // Create a ConcurrentHashMap from the LinkedHashMap
    ConcurrentHashMap<String, Integer> concurrentHashMap = new ConcurrentHashMap<>(linkedHashMap);

    // Print the ConcurrentHashMap
    System.out.println(concurrentHashMap);  // Output: {Apple=1, Banana=2, Cherry=3}
  }
}

In this example, we create a LinkedHashMap and add some key-value pairs to it. We then create a ConcurrentHashMap from the LinkedHashMap using the new ConcurrentHashMap(Map m) constructor. This creates a new ConcurrentHashMap with the same key-value pairs as the LinkedHashMap.

Note that when you create a ConcurrentHashMap from another map, the ConcurrentHashMap will not be thread-safe unless the original map is thread-safe.