Hashing / Mapping question

Question

Hello,
I have an application that creates images based on several integer parameters. In order to speed things up, I want to cash the images in a Map so that I don't need to recreate images whose parameters have already been seen.
Using decimal digits, the ranges of my params are as follows:
1 digit (range 0-3)
3 digits(range 0-999)
4 digits(range 0-4095)
4 digits(range 0-4095)
I want to come up with a unique key based on the possible values of my params. One simple way to do this would be to simply concatenate the values paying attention to 'place value.' So the lowest map value would be zero (all four params 0) and the highest value would be
399940954095 (i.e. 3-999-4095-4095)
but this gives me a value greater than max int.
Can someone suggest a method that would yield a unique integer for each unique combination of my parameters?
Thanks,
Ted

Answer 1

class Key
    private final int a;
    private final int b;
    private final int c;
    private final int d;
    private final int hash;
    public Key(final int a, final int b, final int c, final int d)
        this.a = a;
        this.b = b;
        this.c = c;
        this.d = d;
        hash = a + 29 * b + 47 * c + 59 * d;
    public boolean equals(Object o)
        if (o == null || o.getClass != Key.class) return false;       
        Key other = (Key) o;
        return a == other.a && b == other.b && c == other.c && d == other.d;
    public int hashCode()
        return hash;
}