The java.util.TreeMap.containsKey() method is used to check whether a particular key is being mapped in the TreeMap or not. It takes the key element as a parameter and returns True if that element is mapped in the map.
Syntax:
Tree_Map.containsKey(key_element)
Parameters: The method takes just one parameter key_element that refers to the key whose mapping is supposed to be checked inside a map.
Return Value: The method returns boolean true if the presence of the key is detected else false .
Below programs are used to illustrate the working of java.util.TreeMap.containsKey() Method:
Program 1: Mapping String Values to Integer Keys.
// Java code to illustrate the containsKey() methodimport java.util.*;  public class Tree_Map_Demo {    public static void main(String[] args)    {          // Creating an empty TreeMap        TreeMap<Integer, String> tree_map =         new TreeMap<Integer, String>();          // Mapping string values to int keys        tree_map.put(10, "Geeks");        tree_map.put(15, "4");        tree_map.put(20, "Geeks");        tree_map.put(25, "Welcomes");        tree_map.put(30, "You");          // Displaying the TreeMap        System.out.println("Initial Mappings are: " + tree_map);          // Checking for the key_element '20'        System.out.println("Is the key '20' present? " +         tree_map.containsKey(20));          // Checking for the key_element '5'        System.out.println("Is the key '5' present? " +         tree_map.containsKey(5));    }} |
Initial Mappings are: {10=Geeks, 15=4, 20=Geeks, 25=Welcomes, 30=You}
Is the key '20' present? true
Is the key '5' present? false
Program 2: Mapping Integer Values to String Keys.
// Java code to illustrate the containsKey() methodimport java.util.*;  public class Tree_Map_Demo {    public static void main(String[] args)    {          // Creating an empty TreeMap        TreeMap<String, Integer> tree_map =         new TreeMap<String, Integer>();          // Mapping int values to string keys        tree_map.put("Geeks", 10);        tree_map.put("4", 15);        tree_map.put("Geeks", 20);        tree_map.put("Welcomes", 25);        tree_map.put("You", 30);          // Displaying the TreeMap        System.out.println("Initial Mappings are: " + tree_map);          // Checking for the key_element 'Welcomes'        System.out.println("Is the key 'Welcomes' present? " +         tree_map.containsKey("Welcomes"));          // Checking for the key_element 'World'        System.out.println("Is the key 'World' present? " +         tree_map.containsKey("World"));    }} |
Initial Mappings are: {4=15, Geeks=20, Welcomes=25, You=30}
Is the key 'Welcomes' present? true
Is the key 'World' present? false
Note: The same operation can be performed with any type of Mappings with variation and combination of different data types.
