Funzione di ricerca della tabella Hash Java
Ho creato una tabella hash ma mi sembra di essere bloccato su un problema. Ho dati nella tabella hash e durante la ricerca dei dati restituisce come previsto. Tuttavia, se cerco qualcosa che non è nella tabella ma ancora hash a un elemento che è presente, non restituisce false.
Per esempio: ho Hello come chiave nella mia tabella hash, diciamo elemento 15. Quindi faccio una ricerca per il mondo e hash lo stesso di Hello, solo per esempio.
Quello che mi aspetto il mio il codice da fare è restituire null perché anche se la chiave ha lo stesso hash, non sono uguali. Ma il mio codice qui sotto, restituirà invece la chiave / dati (record) per Hello.
@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;
}
Classe di record
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);
}
}
1 answers
Questo è un classico = = vs .equals () problema.
a[i].record.getKey() != k
può essere vero mentre a[i].record.getKey().equals(k)
è anche vero.
Dovresti usare (!a[i].record.getKey().equals(k))
invece di a[i].record.getKey() != k