JDK源码阅读:实现自己的HashMap

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/*** * 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());    }}
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