I have a class MapEntry to implement Hashmap. I need to implement a method where I can get key from value and method delete. I know that HashMap does not implement such method as getValue but my prof asked to do this. I'm new to programming how it's a little bit hard for me right now. I'll appreciate any help.
public class MapEntry<K,V> {
MapEntry<K,V> next;
K key;
V value;
public MapEntry(K key, V value) {
this.setKey(key);
this.setValue(value);
}
public void setKey( K key){
this.key=key;
}
public void setValue(V value){
this.value=value;
}
public K getKey(){
return key;
}
public V getValue(){
return value;
}
public void setNext(MapEntry<K,V> next) {
this.next = next;
}
public MapEntry<K, V> getNext() {
return next;
}
}
public class HashMap{
private int DEFAULT_CAPACITY = 10;
private MapEntry<String,Double>[] Hash;
private int size;
public HashMap() {
Hash = new MapEntry[DEFAULT_CAPACITY];
}
public boolean isEmpty(){
if(size!= 0){
return false;
}
else{
return true;
}
}
public int getHashCode(String key){
int bucketIndex = key.hashCode()%Hash.length;
return bucketIndex;
}
public Double get(String key){
if(key == null){
try {
throw new IllegalAccessException("Null key");
} catch (IllegalAccessException e) {
e.printStackTrace();
}
}
MapEntry<String,Double> entry = Hash[getHashCode(key)];
while (entry != null && !key.equals(entry.getKey()))
entry = entry.getNext();
if(entry != null)
return entry.getValue();
else
return null;
}
}
public void put(String key, double value){
int keyBucket =hash(key);
MapEntry<String,Double> temp = Hash[keyBucket];
while (temp !=null){
if((temp.key == null && key == null)
|| (temp.key != null && temp.key.equals(key))){
temp.value = value;
return;
}
temp = temp.next;
}
Hash[keyBucket] = new MapEntry<String, Double>(key,value);
size++;
}
public void delete (String key) throws IllegalAccessException {
if(key == null){
throw new IllegalAccessException("Null key");
}
}
private int hash(String key){
if(key == null){
return 0;
}else {
return Math.abs(key.hashCode()% this.Hash.length);
}
}
public static void main(String[] args) {
HashMap hashMap = new HashMap();
hashMap.put("value", 2.2);
hashMap.put("bob", 2.3);
System.out.println(hashMap.get("value"));
System.out.println(hashMap.get("bob"));
System.out.println(hashMap.size);
System.out.println(hashMap.getHashCode("value"));
System.out.println(hashMap.getHashCode("bob"));
System.out.println(hashMap.isEmpty());
}
}
