ConcurrentHashMap get() Method in Java - GeeksforGeeks

14 Sep, 2018
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()
Java - util package
Java-ConcurrentHashMap
Java-Functions
Java
Java
Writing code in comment?
Please use ide.geeksforgeeks.org,
generate link and share the link here.
Arrays in Java
Split() String method in Java with examples
For-each loop in Java
Arrays.sort() in Java with examples
Reverse a string in Java
Initialize an ArrayList in Java
HashMap in Java with Examples
Interfaces in Java
Object Oriented Programming (OOPs) Concept in Java
ArrayList in Java