爲什麼EnumMap內部數組是瞬態的

Question

枚舉映射在內部表示爲數組。 K [] keyUniverse鍵和Object [] vals數組數組。這些陣列是瞬態的。你能告訴我爲什麼嗎？

Answer 1

它們是暫時的，以允許以不同（更好）方式進行序列化。另外entrySet是暫時的。

private void writeObject(java.io.ObjectOutputStream s) 
    throws java.io.IOException 
{ 
    // Write out the key type and any hidden stuff 
    s.defaultWriteObject(); 

    // Write out size (number of Mappings) 
    s.writeInt(size); 

    // Write out keys and values (alternating) 
    for (Map.Entry<K,V> e : entrySet()) { 
     s.writeObject(e.getKey()); 
     s.writeObject(e.getValue()); 
    } 
} 

private void readObject(java.io.ObjectInputStream s) 
    throws java.io.IOException, ClassNotFoundException 
{ 
    // Read in the key type and any hidden stuff 
    s.defaultReadObject(); 

    keyUniverse = getKeyUniverse(keyType); 
    vals = new Object[keyUniverse.length]; 

    // Read in size (number of Mappings) 
    int size = s.readInt(); 

    // Read the keys and values, and put the mappings in the HashMap 
    for (int i = 0; i < size; i++) { 
     K key = (K) s.readObject(); 
     V value = (V) s.readObject(); 
     put(key, value); 
    } 
}