The get() method of java.util.concurrent.ConcurrentHashMap is an in-built function in Java which accepts a key as parameter and returns the value mapped to it. It returns null if no mapping exists for the key passed as parameter.
Syntax:
Concurrent.get(Object key_element)
Parameters: The method accepts a single parameter key_element of object type which refers to the key whose associated value is supposed to be returned.
Return Value: The method returns the value associated with the key_element in the parameter.
Exception: The function throws NullPointerException when the specified key_element is null.
Below programs illustrate the use of java.util.concurrent.ConcurrentHashMap.get() method :
Program 1: This program involves mapping String Values to Integer Keys.
// Java Program Demonstrate get() // method of ConcurrentHashMap import java.util.concurrent.*; class GFG { public static void main(String[] args) { ConcurrentHashMap<Integer, String> chm = new ConcurrentHashMap<Integer, String>(); chm.put( 100 , "Geeks" ); chm.put( 101 , "for" ); chm.put( 102 , "Geeks" ); chm.put( 103 , "Contribute" ); // Displaying the HashMap System.out.println( "The Mappings are: " ); System.out.println(chm); // Display the value of 100 System.out.println( "The Value associated to " + "100 is : " + chm.get( 100 )); // Getting the value of 103 System.out.println( "The Value associated to " + "103 is : " + chm.get( 103 )); } } |
The Mappings are: {100=Geeks, 101=for, 102=Geeks, 103=Contribute} The Value associated to 100 is : Geeks The Value associated to 103 is : Contribute
Program 2: This program involves mapping Integer Values to String Keys.
// Java Program Demonstrate get() // method of ConcurrentHashMap import java.util.concurrent.*; class GFG { public static void main(String[] args) { ConcurrentHashMap<String, Integer> chm = new ConcurrentHashMap<String, Integer>(); chm.put( "Geeks" , 100 ); chm.put( "GFG" , 10 ); chm.put( "GeeksforGeeks" , 25 ); chm.put( "Contribute" , 102 ); // Displaying the HashMap System.out.println( "The Mappings are: " ); System.out.println(chm); // Display the value of Geeks System.out.println( "The Value associated to " + "Geeks is : " + chm.get( "Geeks" )); // Getting the value of Contribute System.out.println( "The Value associated to " + "Contribute is : " + chm.get( "Contribute" )); } } |
The Mappings are: {GeeksforGeeks=25, Geeks=100, GFG=10, Contribute=102} The Value associated to Geeks is : 100 The Value associated to Contribute is : 102
Reference : https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/ConcurrentHashMap.html#get()
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