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:
- 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
- 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.
- 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
- 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
- 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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