java - 实现 reHash() 算法的不同方式

Question

我正在实现一个哈希表，而不使用任何内置的 java HashTable 功能，并收到以下行的编译时错误:

newHashTable.add(reHashValueIndex, bucket.get(j));//insert values into new table

错误:找不到适合 add(int, String) 的方法

我发现 String 与 String 类型的 LinkedLists 的 ArrayList 类型不同，这就是我收到错误的原因，但我可以使用一些帮助来实现 reHash() 的另一种方法

public void reHash(ArrayList<LinkedList<String>> oldHashTable)
{
    ArrayList<LinkedList<String>> newHashTable = new ArrayList(oldHashTable.size()*2);

    //rehash values in oldHashTable
    for (int i = 0; i < (oldHashTable.size()); i++)//loop old hashTable.size number of times 
    {
        bucket = oldHashTable.get(i);//bucket = linkedList at oldHashTable
        if (bucket != null)//if hashTable linkedList bucket element contains elements 
        {
            for (int j = 0; j < bucket.size(); j++)//loop through it 
            {
                if(bucket.get(j) != null)//looking for items
                {
                    int reHashValueIndex = hash(bucket.get(j)); //rehash element 
                    newHashTable.add(reHashValueIndex, bucket.get(j));//insert values into new table at new rehashed index
                }
            }
        }
    }
    //increment expand variable by one
    expand++;
}

Answer 1

newHashTable 的类型为 ArrayList <'LinkedList<'String>>。所以你只能添加LinkedList对象。您可能想要做的是首先重建存储桶，然后将其添加到新的哈希表中。像这样的东西

    public void reHash(ArrayList<LinkedList<String>> oldHashTable)
    {
        ArrayList<LinkedList<String>> newHashTable = new ArrayList(oldHashTable.size()*2);

        //rehash values in oldHashTable
        for (int i = 0; i < (oldHashTable.size()); i++)//loop old hashTable.size number of times 
        {
            bucket = oldHashTable.get(i);//bucket = linkedList at oldHashTable

            if (bucket != null)//if hashTable linkedList bucket element contains elements 

            {
                newBucket = new LinkedList<String>();
                for (int j = 0; j < bucket.size(); j++)//loop through it 
                {
                    if(bucket.get(j) != null)//looking for items
                    {
                        int reHashValueIndex = hash(bucket.get(j)); //rehash element 
                        newBucket.add(reHashValueIndex, bucket.get(j));//insert values into new table at new rehashed index
                    }
                }
            }
            newHashTable.add(newBucket);
        }
        //increment expand variable by one
        expand++;
    }