This Java program is to Implement EnumMap API.A specialized Map implementation for use with enum type keys. All of the keys in an enum map must come from a single enum type that is specified, explicitly or implicitly, when the map is created. Enum maps are represented internally as arrays. This representation is extremely compact and efficient.
Enum maps are maintained in the natural order of their keys (the order in which the enum constants are declared).
Here is the source code of the Java program to Implement EnumMap API. The Java program is successfully compiled and run on a Linux system. The program output is also shown below.
import java.util.Collection; import java.util.EnumMap; import java.util.Iterator; import java.util.Map; import java.util.Map.Entry; import java.util.Set; public class EnumMapImpl<K extends Enum<K>, V> { private EnumMap<K, V> enumMap; /** Creates an empty enum map with the specified key type. **/ public EnumMapImpl(Class<K> keyType) { enumMap = new EnumMap<K, V>(keyType); } /** * Creates an enum map with the same key type as the specified enum map, * initially containing the same mappings (if any). **/ public EnumMapImpl(EnumMap<K, ? extends V> m) { enumMap = new EnumMap<K, V>(m); } /** Creates an enum map initialized from the specified map. **/ public EnumMapImpl(Map<K, ? extends V> m) { enumMap = new EnumMap<K, V>(m); } /** Removes all of the mappings from this map. **/ public void clear() { enumMap.clear(); } /** Returns true if this map contains a mapping for the specified key. **/ public boolean containsKey(Object key) { return enumMap.containsKey(key); } /** Returns true if this map maps one or more keys to the specified value. **/ public boolean containsValue(Object value) { return enumMap.containsValue(value); } /** Returns a Set view of the mappings contained in this map. **/ public Set<Map.Entry<K, V>> entrySet() { return enumMap.entrySet(); } /** Returns a Set view of the keys contained in this map. **/ public Set<K> keySet() { return enumMap.keySet(); } /** * Returns the value to which the specified key is mapped, or null if this * map contains no mapping for the key. **/ public V get(Object key) { return enumMap.get(key); } /** Associates the specified value with the specified key in this map. **/ public V put(K key, V value) { return enumMap.put(key, value); } /** Copies all of the mappings from the specified map to this map. **/ public void putAll(Map<? extends K, ? extends V> map) { enumMap.putAll(map); } /** Removes the mapping for this key from this TreeMap if present. **/ public V remove(Object key) { return enumMap.remove(key); } /** Returns the number of key-value mappings in this map. **/ public int size() { return enumMap.size(); } /** Returns a Collection view of the values contained in this map. **/ public Collection<V> values() { return enumMap.values(); } /** Returns true if this map contains no key-value mappings. **/ public boolean isEmpty() { return enumMap.isEmpty(); } public enum NUMBER { FIRST, SECOND, THIRD, FOURTH; } public static void main(String... arg) { EnumMapImpl<NUMBER, Integer> enumMap = new EnumMapImpl<NUMBER, Integer>(NUMBER.class); enumMap.put(NUMBER.FIRST, 100); enumMap.put(NUMBER.SECOND, 200); enumMap.put(NUMBER.THIRD, 300); System.out.println("the key set of the enumMap is "); Set<NUMBER> keySet = enumMap.keySet(); Iterator<NUMBER> itr = keySet.iterator(); while (itr.hasNext()) { System.out.print(itr.next() + "\t"); } System.out.println(); System.out.println("the values of the enumMap is "); Collection<Integer> collectionValues = enumMap.values(); Iterator<Integer> itr2 = collectionValues.iterator(); while (itr2.hasNext()) { System.out.print(itr2.next() + "\t"); } System.out.println(); System.out.println("the entry set of the enumMap is "); Iterator<Entry<NUMBER, Integer>> eitr; Set<Entry<NUMBER, Integer>> entrySet = enumMap.entrySet(); eitr = entrySet.iterator(); while (eitr.hasNext()) { System.out.println(eitr.next() + "\t"); } System.out.println("the enumMap contains Key THIRD :" + enumMap.containsKey(NUMBER.THIRD)); System.out.println("the enumMap contains Value 600 :" + enumMap.containsValue(600)); System.out.println("the size of the enumMap is " + enumMap.size()); enumMap.clear(); if (enumMap.isEmpty()) System.out.println("the enumMap is empty"); else System.out.println("the enumMap is not empty"); } }
$ javac EnumMapImpl.java $ java EnumMapImpl the key set of the enumMap is FIRST SECOND THIRD the values of the enumMap is 100 200 300 the entry set of the enumMap is FIRST=100 SECOND=200 THIRD=300 the enumMap contains Key THIRD :true the enumMap contains Value 600 :false the size of the enumMap is 3 the enumMap is empty
Related posts:
Java 8 Stream findFirst() vs. findAny()
How to Get the Last Element of a Stream in Java?
Java Program to Check whether Graph is a Bipartite using BFS
LIKE Queries in Spring JPA Repositories
Enum trong java
Finding the Differences Between Two Lists in Java
Java Program to Find SSSP (Single Source Shortest Path) in DAG (Directed Acyclic Graphs)
A Guide to Iterator in Java
Guide to Spring 5 WebFlux
Java Program to Perform Stooge Sort
Collection trong java
Java – Random Long, Float, Integer and Double
Java Program to Implement Weight Balanced Tree
Guide to the Java Queue Interface
Hướng dẫn Java Design Pattern – Null Object
Spring Data JPA Delete and Relationships
Java Program to Implement ArrayDeque API
Simplify the DAO with Spring and Java Generics
Java Program to Search for an Element in a Binary Search Tree
Hashing a Password in Java
Spring Security Registration – Resend Verification Email
Apache Camel with Spring Boot
New Features in Java 8
HashMap trong Java hoạt động như thế nào?
Guide to Java 8’s Collectors
Handle EML file with JavaMail
Spring Boot With H2 Database
Java Program to Implement Double Order Traversal of a Binary Tree
Ways to Iterate Over a List in Java
Lập trình đa luồng với CompletableFuture trong Java 8
Java Program to Check whether Graph is a Bipartite using DFS
SOAP Web service: Upload và Download file sử dụng MTOM trong JAX-WS