Map.Entry interface in Java with example

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

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

// 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());
        }
    }
}

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