AbstractMap keySet() Method in Java with Examples

Last Updated : 26 Oct, 2018
The AbstractMap.keySet() method in Java is used to create a set out of the key elements contained in the abstract map. It basically returns a set view of the keys or we can create a new set and store the key elements in them. Syntax: 
AbstractMap.keySet()
Parameters: The method does not take any parameter. Return Value: The method returns a set having the keys of the abstract map. Below programs are used to illustrate the working of AbstractMap.keySet() Method: Program 1: Mapping String Values to Integer Keys. Java 
// Java code to illustrate the keySet() 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);

        // Using keySet() to get
        // the set view of keys
        System.out.println("The set is: "
                           + abs_map.keySet());
    }
}
Output: 
Initial Mappings are: {20=Geeks, 25=Welcomes, 10=Geeks, 30=You, 15=4}
The set is: [20, 25, 10, 30, 15]
Program 2: Mapping Integer Values to String Keys. Java 
// Java code to illustrate the keySet() 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);

        // Using keySet() to get the set view of keys
        System.out.println("The set is: "
                           + abs_map.keySet());
    }
}
Output: 
Initial Mappings are: {4=15, Geeks=20, You=30, Welcomes=25}
The set is: [4, Geeks, You, Welcomes]
Note: The same operation can be performed with any type of Mappings with variation and combination of different data types.
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