Question

我创建了一个哈希表，但我似乎陷入了一个问题。我在哈希表中有数据，当搜索数据时，它会按预期返回。但是，如果我搜索不在表中但仍然散列到存在的元素的内容，则它不会返回false。

例如：我将Hello作为哈希表中的一个键，让我们说元素15.然后我会搜索World，它的哈希值与Hello相同，例如。

我希望我的代码可以返回null，因为即使键的哈希值相同，它们也不相等。但是我的代码如下，将返回Hello的密钥/数据（记录）。

 @SuppressWarnings("rawtypes")
public Record search(T k) {
    int i = hash(k);//Assign the computed hash value (combination of Record Class hashCode and Table's hash function above) to i.
    if (a[i] == null || a[i].record.equals(k)) { 
        return null; 
    } else if (!a[i].record.equals(i) && a[i].record.getKey() != k) {//otherwise, the record is found and if the key stored does not equal the key being searched return null
        return a[i].record;
    } else { //otherwise the record is not the first record in the linked list
        cursor = a[i]; //set cursor to equal the entire list of records sorted a the hash key reference
        if (cursor.record.getKey() != k) { //if the key at cursor.record does not equal key (k), then move onto the cursor.next
            return cursor.next.record;
        }
    }
    return null;
}

记录课程

public class Record<T, U> {

private T key;//Contacts name, and the value that is ultimately hashed. It is then inserted, searched and deleted
private U data;//This data is the Contacts address, when the key is hashed, nothing is done to this value except that it is 
//either stored or retrieved from the hash table when the key is used

public T getKey() {
    return key;//returns the value stored as a key
}

public void setKey(T k) {
    this.key = k;//used during the insert operation to set key's value.
}

public U getData(T k) {//retrieve the data that is stored with an associated key that has been updated, searhed or is being written to a file
    return data;
}

public void setData(U data) {//adds the data to the records data element
    this.data = data;
}

public int hashCode(T k) {//When this hash code function is called, it returns a mathematical representation of the key, that was passed to it
    //it returns the absolute value of the generic hashCode() function. Further computations are required in the Table class, since the hash created here
    //can be very large and would throw and exception.  For example, the hash for "Chris" after this computation has been performed is 94639767, which is
    //much larger than our array. So this will cause an IndexOutOfBoundsException().
    return Math.abs(k.hashCode());
}

public boolean equals(Record<T, U> r) {
    //this equals method, doesn't override the generic equals() method provided by Java. Instead, this method is created to use instead of the generic
    //equals method. When this is called, the has value computed above, with the additional math from the Table class, is compared to all of the elements
    //in the array. If a match is found, this returns true
    return key.equals(r.key);
}
}

Answer 1

这是一个经典的== vs .equals（）问题。

a[i].record.getKey() != k可以为真，而a[i].record.getKey().equals(k)也是如此。

您应该使用(!a[i].record.getKey().equals(k))代替a[i].record.getKey() != k

Java哈希表搜索功能

1 个答案: