Java hashCode method maximum return value

Question

Can someone tell me what are the maximum and minimum int values that the Java String.hashCode() method can return?

Solution 1

String.hashCode () return an int calculated by using the below formula:

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 i-th character of the string, n is the length of the string, and ^ indicates exponentiation. (The hash value of the empty string is zero.)

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The minimum and max value can be found with the below constants.

 System.out.println (java.lang.Integer.MAX_VALUE); //  2147483647
 System.out.println (java.lang.Integer.MIN_VALUE); // -2147483648

Solution 2

Java int is 4 bytes, signed (two's complement). -2,147,483,648 to 2,147,483,647. Like all numeric types ints may be cast into other numeric types (byte, short, long, float, double). When lossy casts are done (e.g. int to byte) the conversion is done modulo the length of the smaller type.

Solution 3

From the documentation, given that the power to which something is raised depends on the length of the String (which is practically unlimited, as far as I know), I would say that the maximum and minimum must be Integer.MAX_VALUE (2^31 - 1) and Integer.MIN_VALUE (-2^31), respectively.