AbstractMap putAll() Method in Java with Examples

The AbstractMap.putAll() is an inbuilt method of AbstractMap class that is used for the copy operation. The method copies all of the elements i.e., the mappings, from one map into another.

Syntax:

new_abstract_map.putAll(exist_abstract_map)

Parameters: The method takes one parameter exist_abstract_map that refers to the existing map we want to copy from.

Return Value: The method does not return any values.

Exception: The method throws NullPointerException if the map we want to copy from is NULL.

Below programs illustrates the working of AbstractMap.putAll() method:

Program 1: Mapping String Values to Integer Keys.

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// Java code to illustrate the putAll() method
  
import java.util.*;
  
public class Abstract_Map_Demo {
    public static void main(String[] args)
    {
  
        // Creating an empty AbstractMap
        AbstractMap<Integer, String>
            abs_map = new HashMap<Integer, String>();
  
        // Mapping string values to int keys
        abs_map.put(10, "Geeks");
        abs_map.put(15, "4");
        abs_map.put(20, "Geeks");
        abs_map.put(25, "Welcomes");
        abs_map.put(30, "You");
  
        // Displaying the AbstractMap
        System.out.println("Initial Mappings are: "
                           + abs_map);
  
        // Creating a new abstract map and copying
        AbstractMap<Integer, String>
            new_abs_map = new HashMap<Integer, String>();
  
        new_abs_map.putAll(abs_map);
  
        // Displaying the final AbstractMap
        System.out.println("The new map looks like this: "
                           + new_abs_map);
    }
}

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Output:

Initial Mappings are: {20=Geeks, 25=Welcomes, 10=Geeks, 30=You, 15=4}
The new map looks like this: {25=Welcomes, 10=Geeks, 20=Geeks, 30=You, 15=4}

Program 2: Mapping Integer Values to String Keys.

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// Java code to illustrate the putAll() method
  
import java.util.*;
  
public class Abstract_Map_Demo {
    public static void main(String[] args)
    {
  
        // Creating an empty AbstractMap
        AbstractMap<String, Integer>
            abs_map = new HashMap<String, Integer>();
  
        // Mapping int values to string keys
        abs_map.put("Geeks", 10);
        abs_map.put("4", 15);
        abs_map.put("Geeks", 20);
        abs_map.put("Welcomes", 25);
        abs_map.put("You", 30);
  
        // Displaying the AbstractMap
        System.out.println("Initial Mappings are: "
                           + abs_map);
  
        // Creating a new hash map and copying
        AbstractMap<String, Integer>
            new_abs_map = new HashMap<String, Integer>();
  
        new_abs_map.putAll(abs_map);
  
        // Displaying the final AbstractMap
        System.out.println("The new map looks like this: "
                           + new_abs_map);
    }
}

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Output:

Initial Mappings are: {4=15, Geeks=20, You=30, Welcomes=25}
The new map looks like this: {Geeks=20, 4=15, You=30, Welcomes=25}

Note: The same operation can be performed with any type of Mappings with variation and combination of different data types.



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