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Java / Object, Class and Package

Good implementation of hashCode method in Java.

As per the expert's recommendation, the below steps are listed.

  • Create a int hashcodeResult and assign it a non-zero value.
  • For every field f tested in the equals method,calculates its hash code value c using the following.
    • If the field f is a boolean: calculate (f ? 0 : 1);
    • If the field f is a byte, char, short or int: calculate (int)f;
    • field f is a long, calculate (int)(f ^ (f >>> 32));
    • field f is a float, calculate Float.floatToIntBits(f);
    • field f is a double, calculate Double.doubleToLongBits(f) and use the long value;
    • If the field f is an object: Use the result of the hashCode() method or 0 if f == null;
    • If the field f is an array, consider every field as separate element and calculate the hash value in a recursive fashion and combine the values.
  • Combine the hash value c with hashcodeResult. hashcodeResult=37+c+ hashcodeResult.
  • Return the value of hashcodeResult.

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