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Map containsKey() method in Java with Examples

Last Updated : 31 Dec, 2018
The java.util.Map.containsKey() method is used to check whether a particular key is being mapped into the Map or not. It takes the key element as a parameter and returns True if that element is mapped in the map. Syntax: 
boolean 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.Map.containsKey() Method: Program 1: Mapping String Values to Integer Keys.
Output: 
Initial Mappings are: {20=Geeks, 25=Welcomes, 10=Geeks, 30=You, 15=4}
Is the key '20' present? true
Is the key '5' present? false
Program 2: Mapping Integer Values to String Keys.
Output: 
Initial Mappings are: {4=15, Geeks=20, You=30, Welcomes=25}
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. Reference: https://docs.oracle.com/javase/7/docs/api/java/util/Map.html#containsKey(java.lang.Object)
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