Home » Java programming language

Java TreeMap putAll() Method with Example

TreeMap Class putAll() method: Here, we are going to learn about the putAll() method of TreeMap Class with its syntax and example.
Submitted by Preeti Jain, on February 29, 2020

TreeMap Class putAll() method

• putAll() method is available in java.util package.
• putAll() method is used to copy all the key-value pairs from the given map (m) and paste it into this map.
• putAll() method is a non-static method, it is accessible with the class object only and if we try to access the method with the class name then we will get an error.
• putAll() method may throw an exception at the replacing mappings.
  • ClassCastException: This exception may throw when the given map (m) elements protect it from being saved in this Map.
  • NullPointerException: This exception may throw when the given parameter is null exists.

Syntax:

    public void putAll(Map m);

Parameter(s):

• Map m – represents the mappings to be saved in this TreeMap.

Return value:

The return type of the method is void, it returns nothing.

Example:

// Java program to demonstrate the example 
// of void putAll(Map m) method of TreeMap 

import java.util.*;

public class PutAllOfTreeMap {
    public static void main(String[] args) {
        // Instantiates two TreeMap
        TreeMap < Integer, String > tm1 = new TreeMap < Integer, String > ();
        TreeMap < Integer, String > tm2 = new TreeMap < Integer, String > ();

        // By using put() method is
        // to put the key-value pairs in
        // treemap tm1
        tm1.put(1, "C");
        tm1.put(4, "C++");
        tm1.put(3, "Java");
        tm1.put(2, "Php");

        // By using put() method is
        // to put the key-value pairs in
        // treemap tm2
        tm2.put(1, "SQL");
        tm2.put(2, "DBMS");

        // Display TreeMap tm1
        System.out.println("tm1: " + tm1);

        // By using putAll() method is to
        // put all the elements of tm2 in tm1
        tm1.putAll(tm2);

        // Display updated TreeMap tm1
        System.out.println("tm1.putAll(tm2): " + tm1);
    }
}

Output

tm1: {1=C, 2=Php, 3=Java, 4=C++}
tm1.putAll(tm2): {1=SQL, 2=DBMS, 3=Java, 4=C++}