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Map.Entry interface in Java with example

Last Updated : 02 Nov, 2022
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Map.Entry interface in Java provides certain methods to access the entry in the Map. By gaining access to the entry of the Map we can easily manipulate them. Map.Entry is a generic and is defined in the java.util package.

Declaration :

Interface Map.Entry
k -> Key
V -> Value

Methods:

  1. equals (Object o) – It compares the object (invoking object) with the Object o for equality.
    Syntax :

    boolean equals(Object o)
Parameters :
o -> Object to which we want to compare
Returns:
true: if both objects are equals
false: otherwise
  2. K getKey() – Returns the key for the corresponding map entry.
    Syntax :

    K getKey()
Parameters :
-------------
Returns:
K -> Returns the corresponding Key of a entry on which it is invoked

    Exception –

    • IllegalStateException is thrown when entry has been removed from the map.
  3. V getValue() – Returns the value for the corresponding map entry.
    Syntax :

    V getValue()
Parameters :
-------------
Returns:
V -> Returns the corresponding value of a entry on which it is invoked
  4. int hashcode() – Returns the hashcode for the corresponding map entry.
    Syntax :

    int hashcode()
Parameters :
-------------
Returns:
int -> Returns the hash-code of entry on which it is invoked
  5. V setValue(V v) – Sets the value of the map with specified value v 
    V setValue(V v)
Parameters :
v -> Value which was earlier stored in the entry on which it is invoked
Returns:
int -> Returns the hash-code of a entry on which it is invoked

    Exception :

    • ClassCastException is thrown if the class of the value ‘v’ is not a correct type for map.
    • NullPointerException is thrown if ‘null’ is stored in ‘v’, and ‘null ’ is not supported by map.
    • UnsupportedOperationException is thrown if we cannot manipulate the map or the put operation is not supported by the map.
    • IllegalArgumetException is thrown If there is some problem with the argument i.e v
    • IllegalStateException is thrown when entry has been removed from the map

Set<Map.Entry> entrySet() – Returns the Set view of the entire map.
Note : This is not a method of Map.entry interface but it is discussed here because this method is useful while working with Map.Entry interface.

Set<Map.Entry> entrySet() 
Parameters :
---------------
Returns:
Set<Map.Entry> ->: Returns a Set containing the Map.Entry values

Program below demonstrate the working of Map.Entry:




// Java Program to demonstrate the
// methods of Map.Entry 
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;
  
public class GFG 
{
    public static void main(String[] args) 
    {
        // Create a LinkedHashMap
        LinkedHashMap<String,Integer> m = 
                new LinkedHashMap<String, Integer>();
          
        m.put("1 - Bedroom" , 25000);
        m.put("2 - Bedroom" , 50000);
        m.put("3 - Bedroom" , 75000);
        m.put("1 - Bedroom - hall", 65000);
        m.put("2 - Bedroom - hall", 85000);
        m.put("3 - Bedroom - hall", 105000);
          
        // Using entrySet() to get the entry's of the map
        Set<Map.Entry<String,Integer>> s = m.entrySet();
          
        for (Map.Entry<String, Integer> it: s)
        {
            // Using the getKey to get key of the it element
            // Using the getValue to get value of the it element
            System.out.println("Before change of value = " + 
                       it.getKey() + "   " +  it.getValue());
              
            // Changing the value of 1 - Bedroom.
            double getRandom = Math.random() * 100000;
            int getRoundoff = (int) Math.round(getRandom);
                  
            // Using setValue to change the value of the
            // map element
            it.setValue(getRoundoff);
              
            System.out.println("After change of value = " + 
                       it.getKey() + "   " + it.getValue());
        }
    }
} 






                        








Output:


Before change of value = 1 - Bedroom   25000
After change of value = 1 - Bedroom   59475
Before change of value = 2 - Bedroom   50000
After change of value = 2 - Bedroom   51650
Before change of value = 3 - Bedroom   75000
After change of value = 3 - Bedroom   95200
Before change of value = 1 - Bedroom - hall   65000
After change of value = 1 - Bedroom - hall   74112
Before change of value = 2 - Bedroom - hall   85000
After change of value = 2 - Bedroom - hall   41490
Before change of value = 3 - Bedroom - hall   105000
After change of value = 3 - Bedroom - hall   10902






                                    


                                                                          

                                        

                                                                              

                                                                        

                                        

                                            

                                                

                                                    

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