Java Creating HashMap from Other Maps

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

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

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

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

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

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

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

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

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

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

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

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