Java Map Interface
Map interface keys and values-one mapping. You can get the value by key.
- Given a key and a value, you can store the value after a Map object, you can access the corresponding value through the key.
- When the value of access does not exist, the method will throw an exception NoSuchElementException.
- When the object type and in the Map element type is not compatible with the time, it will throw a ClassCastException.
- When using Null Null objects are not allowed in the Map object, throws a NullPointerException.
- When the attempt to modify a read-only Map, throws an UnsupportedOperationException.
No. | Method Description |
---|---|
1 | void clear () Removes all of the mappings (optional) map. |
2 | boolean containsKey (Object k) If this map contains a mapping between the specified key, it returns true. |
3 | boolean containsValue (Object v) If this map maps one or more keys to the specified value, it returns true. |
4 | Set entrySet () Back Set view of the mappings contained in this map. |
5 | boolean equals (Object obj) Compares the specified object with this map for equality. |
6 | Object get (Object k) Returns the value of the specified key is mapped; if this map contains no mapping for the key, it returns null. |
7 | int hashCode () Returns the hash code value for this map. |
8 | boolean isEmpty () If this map contains no key - value mappings, it returns true. |
9 | Set keySet () Back Set view this map contains keys. |
10 | Object put (Object k, Object v) Associated with the specified key to the specified value to this map (optional operation). |
11 | void putAll (Map m) Copy specify the mapping in all of the mappings from this map (optional operation). |
12 | Object remove (Object k) If there is a mapping between keys, it is removed from (optional) map. |
13 | int size () Returns map key - value mappings. |
14 | Collection values () Returns a Collection view of the values contained in this map. |
Examples
The following example to explain the function Map
import java.util.*; public class CollectionsDemo { public static void main(String[] args) { Map m1 = new HashMap(); m1.put("Zara", "8"); m1.put("Mahnaz", "31"); m1.put("Ayan", "12"); m1.put("Daisy", "14"); System.out.println(); System.out.println(" Map Elements"); System.out.print("\t" + m1); } }
The above examples compiled results are as follows:
Map Elements {Mahnaz=31, Ayan=12, Daisy=14, Zara=8}