HashMap containsKey() Method in Java The java. util. HashMap. containsKey() method is used to check whether a particular key is being mapped into the HashMap or not . It takes the key element as a parameter and returns True if that element is mapped in the map.
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Get keys from value in HashMap To find all the keys that map to a certain value, we can loop the entrySet() and Objects. equals to compare the value and get the key .
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