代码
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| public class CustomHashMap<K, V> {
private class Entry<K, V> {
int hash;
K key;
V value;
Entry<K, V> next;
Entry(int hash, K key, V value, Entry<K, V> next) {
this.hash = hash;
this.key = key;
this.value = value;
this.next = next;
}
}
private static final int DEFAULT_CAPACITY = 1 << 4;
private Entry<K, V>[] table;
private int capacity;
private int size;
public CustomHashMap() {
this(DEFAULT_CAPACITY);
}
public CustomHashMap(int capacity) {
if (capacity < 0) {
throw new IllegalArgumentException();
} else {
table = new Entry[capacity];
size = 0;
this.capacity = capacity;
}
}
public int size() {
return size;
}
public boolean isEmpty() {
return size == 0 ? true : false;
}
private int hash(K key) {
int i = key.hashCode() & (capacity - 1);
double tmp = key.hashCode() * (Math.pow(5, 0.5) - 1) / 2;
double digit = tmp - Math.floor(tmp);
return (int) Math.floor(digit * capacity);
}
public void put(K key, V value) {
if (key == null) {
throw new IllegalArgumentException();
}
int hash = hash(key);
Entry<K, V> nEntry = new Entry<K, V>(hash, key, value, null);
Entry<K, V> entry = table[hash];
while (entry != null) {
if (entry.key.equals(key)) {
entry.value = value;
return;
}
entry = entry.next;
}
nEntry.next = table[hash];
table[hash] = nEntry;
size++;
}
public V get(K key) {
if (key == null) {
throw new IllegalArgumentException();
}
int hash = hash(key);
Entry<K, V> entry = table[hash];
while (entry != null) {
if (entry.key.equals(key)) {
return entry.value;
}
entry = entry.next;
}
return null;
}
public static void main(String[] args) {
CustomHashMap<String, String> map = new CustomHashMap<String, String>();
map.put("1", "11");
map.put("1", "22");
map.put("3", "33");
System.out.println(map.get("1"));
}
}
|
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