String hashCode() method, equals method comparision

• hashCode

  public int hashCode()

  Returns a hash code for this string. The hash code for a String object is computed as

   s[0]*31^(n-1) + s[1]*31^(n-2) + ... + s[n-1]
  

  using int arithmetic, where s[i] is the ith character of the string, n is the length of the string, and ^ indicates exponentiation. (The hash value of the empty string is zero.)

Ideally, the hash function will assign each key to a unique bucket, but this situation is rarely achievable in practice (usually some keys will hash to the same bucket.

hashCode() vs equals() Method

1. If object1 and object2 are equal according to their equals() method, they must also have the same hash code.
2. If object1 and object2 have the same hash code, they do NOT have to be equal too.