How do you reverse a map in Java?

How do you reverse a map in Java?

  1. // Generic method to sort map in Java by the reverse ordering of its keys. public static TreeMap sortByKeys(Map map) {
  2. TreeMap treeMap = Maps. newTreeMap( (Comparator) Ordering. natural(). reverse());
  3. treeMap. putAll(map);
  4. return treeMap; }

Can we get key from value in HashMap?

Get keys from value in HashMap To find all the keys that map to a certain value, we can loop the entrySet() and Objects. equals to compare the value and get the key. The common mistake is use the entry. getValue().

How do you reverse the order of a map?

To reverse the order of a Map object:

  1. Use the Array. from() method to convert the Map to array.
  2. Call the reverse() method to reverse the array.
  3. Pass the result to the Map() constructor.
  4. The new Map will contain the elements in reverse order.

How do you reverse a list in Java without reverse function?

Example to reverse string in Java by using static method

  1. import java.util.Scanner;
  2. public class ReverseStringExample3.
  3. {
  4. public static void main(String[] arg)
  5. {
  6. ReverseStringExample3 rev=new ReverseStringExample3();
  7. Scanner sc=new Scanner(System.in);
  8. System.out.print(“Enter a string : “);

How do you reverse a collection list?

In short, to reverse the order of a List you should:

  1. Create a new ArrayList.
  2. Populate the list with elements, with the add(E e) API method of the ArrayList.
  3. Reverse the elements of the list, invoking the reverse(List list) API method of the Collections.

What is Bimap in Java?

A bimap (or “bidirectional map”) is a map that preserves the uniqueness of its values as well as that of its keys. This constraint enables bimaps to support an “inverse view”, which is another bimap containing the same entries as this bimap but with reversed keys and values.

What is entry and entrySet in Java?

HashMap. entrySet() method in Java is used to create a set out of the same elements contained in the hash map. It basically returns a set view of the hash map or we can create a new set and store the map elements into them. Syntax: hash_map.entrySet() Parameters: The method does not take any parameter.