JDK源码阅读:实现自己的HashMap

/***
* 自己实现的一个简单的HashMap<br>
*
* @author jay
*
* @param <K>
* @param <V>
*/
public class MyHashMap<K, V>
{
private Entry[] table;
private static int capacity = 16;

public MyHashMap()
{
this(capacity);
}

public MyHashMap(int capa)
{
table = new Entry[16];
}

static class Entry<K, V>
{
K key;
V value;
Entry next;

public Entry(K k, V v, Entry ne)
{
this.key = k;
this.value = v;
this.next = ne;
}

public Entry(K k, V v)
{
this.key = k;
this.value = v;
this.next = null;

}

public K getKey()
{
return key;
}

public void setKey(K key)
{
this.key = key;
}

public V getValue()
{
return value;
}

public void setValue(V value)
{
this.value = value;
}

public String toString()
{
if (next == null)
return key + "=" + value;
else
return key + "=" + value + " -> " + next.toString();
}

}

static final int hash(Object key)
{
int h;
return (key == null) ? 0 : (h = key.hashCode()) ^ (h >>> 16);
}

public V put(K key, V value)
{
V oldValue = null;
int index = (capacity - 1) & hash(key);
// int index = Math.abs(key.hashCode() % capacity);
if (table[index] == null)
table[index] = new Entry<K, V>(key, value);

Entry<K, V> pair = new Entry(key, value);
boolean found = false;

for (Entry e = (Entry) table[index]; e != null; e = e.next)
{
Entry<K, V> ipair = e;
if (ipair.getKey().equals(key))
{
oldValue = ipair.getValue();
e.setValue(value);
found = true;
break;
}
}

if (!found)
{
Entry entry = (Entry) table[index];
pair.next = entry;
table[index] = pair;
}
return oldValue;
}

public V get(Object key)
{
int index = Math.abs(key.hashCode() % capacity);
if (table[index] == null)
return null;

for (Entry e = (Entry) table[index]; e != null; e = e.next)
{
if (key.equals(e.getKey()))
return (V) e.getValue();
}

return null;
}

public String toString()
{
if (table == null || table.length == 0)
return null;

StringBuilder builder = new StringBuilder("{\n");
for (int i = 0; i < table.length; i++)
{
Entry e = table[i];
if (e != null)
{
builder.append(e.toString() + "\n");

}
// for (Entry e = table[i]; e != null; e = e.next)
}

builder.append("}");
return builder.toString();
}

public static void main(String[] ar)
{
MyHashMap<Integer, String> map = new MyHashMap<Integer, String>();
for (int i = 1; i < 96; i++)
map.put(i, "zhangjie_" + i);
System.out.println(map.toString());
}
}