java hash code in ruby

string_hash_code.rb

class String
  def java_hash_code
    size = self.size
    hash = 0
    self.chars.each_with_index do |ch, i|
      hash += 31 * ch.ord ** (size - (i + 1))
    end
    [hash].pack("L")
  end
end


puts 'Hello World'.java_hash_code

I believe that you have the exponent backwards and that it should instead be:

class String
  def java_hash_code
    size = self.size
    hash = 0
    self.chars.each_with_index do |ch, i|
      hash += ch.ord * (31 ** (size-(i+1)))
    end
    hash
  end
end

This returns same result as java hashCode() does

TWO_31 = 2 ** 31
TWO_32 = 2 ** 32

def java_hash_code(str)
  size = str.size
  hash = 0
  str.chars.each_with_index do |ch, i|
    hash += ch.ord * (31 ** (size-(i+1)))
    hash = hash % TWO_32 - TWO_31
  end
  hash
end