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() method import 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() method import 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.
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