所以hashmap是java中map结构的基于hash的实现。我已经想出了如何让 hashmap put 方法工作,但是我想编写一个删除键值对的方法,但我在实现它时遇到了麻烦。
我现在唯一能真正理解的是如何告诉函数在密钥为空或不存在的情况下停止。我希望得到任何帮助。关于该方法如何工作的解释或一些基本的伪代码示例将不胜感激。
到目前为止,这就是我在 delete 方法中所拥有的:
public void delete(K key) {
if (key == null) {
throw new IllegalArgumentException("Null Key!");
}
// Implement this method
}
如果有帮助,这是我完成的地图条目类:
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;
}
}
此外,如果有帮助,这是我的 HashMap 类的全部内容。
public class HashMap<K, V> {
private int DEFAULT_CAPACITY = 10;
private MapEntry<K, V>[] Hash;
private int size;
public HashMap() {
Hash = new MapEntry[DEFAULT_CAPACITY];
}
public int getHashCode(K key) {
int bucketIndex = key.hashCode() % Hash.length;
return bucketIndex;
}
public V get(K key) {
if (key == null) {
throw new IllegalArgumentException("Null Key!");
}
MapEntry<K, V> entry = Hash[getHashCode(key)];
while (entry != null && !key.equals(entry.getKey()))
entry = entry.getNext();
if (entry != null)
return entry.getValue();
else
return null;
}
/**
*
* @param key
* @param value
* The put method works by associating the specified value with
* the given key in the map.
* If the key is already in the map,
* the old value is replaced with the new one.
*/
public void put(K key, V value) {
int keyBucket = hash(key);
MapEntry<K, V> 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<K, V>(key, value);
size++;
}
public void delete(K key) {
if (key == null) {
throw new IllegalArgumentException("Null Key!");
}
// Implement this method
}
public void print(){
//Bonus Method
}
private int hash(K key) {
if (key == null) {
return 0;
} else {
return Math.abs(key.hashCode() % this.Hash.length);
}
} }