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 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 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.
