How to Copy Key-Value Pairs from One TreeMap to Another in Java?

In Java, a TreeMap is a Map implementation that stores key-value pairs in a red-black tree structure. It allows insertions and deletions of key-value pairs due to its tree implementation. These operations take O(log n) time on average.

In this article, we will be learning how to copy key-value pairs from one TreeMap to another in Java.

Syntax:

newTreeMap.putAll(originalTreeMap);

This will copy all the key-value pairs from originalTreeMap to newTreeMap.

Program to Copy Key-Value Pairs from One TreeMap to Another in Java

To copy key-value pairs from one TreeMap to another, we can use putAll() method. Below is the code implementation for this:

// Java program to copy key-value pairs from one TreeMap to another using putAll()
import java.util.TreeMap;

public class CopyTreeMap {
    public static void main(String[] args) 
    {
        // Create the course TreeMap
        TreeMap<String, Integer> courseTreeMap = new TreeMap<>();
        courseTreeMap.put("Core Java", 10000);
        courseTreeMap.put("Spring Boot", 20000);
        courseTreeMap.put("AWS", 25000);
        
        // Print the course TreeMap
        System.out.println("Course TreeMap: " + courseTreeMap);

        // Create the another TreeMap
        TreeMap<String, Integer> newCourseTreeMap = new TreeMap<>();

        // Copy key-value pairs using putAll() method
        newCourseTreeMap.putAll(courseTreeMap);

        // Print the newCourse TreeMap
        System.out.println("New Course TreeMap: " + newCourseTreeMap);
    }
}

Course TreeMap: {AWS=25000, Core Java=10000, Spring Boot=20000}
New Course TreeMap: {AWS=25000, Core Java=10000, Spring Boot=20000}

Explanation of the above Program:

• In the above program, it creates an original TreeMap with course names and fees as keys and values.
• A new empty TreeMap is created to copy the data to.
• We have used the putAll() method to copy all key-value pairs from the original map to the new map.
• This copies the entire contents of one map to another map in one line.
• Printing both maps verifies the data is successfully copied from one to the other.
  

Note: putAll() method to easily copy all elements from one TreeMap to another in a single line of code