Re: Unique Long for Map

From:

Mark Space <markspace@sbc.global.net>

Newsgroups:

comp.lang.java.programmer

Date:

Mon, 10 Mar 2008 22:32:25 -0700

Message-ID:

<SPoBj.97$qT6.4@nlpi070.nbdc.sbc.com>

caultonpos@gmail.com wrote:

Is there a well defined method to create a single unique number based
upon two values?

I totally agree with Roedy and Eric here. I think this works, I didn't
actually try it. And I should use generics.

public class SomeClass{
    private HashMap hashTable = new HashMap();

    private static class HashEntry {
        long long1;
        long long2;

         public HashEntry(long long1, long long2) {
             this.long1 = long1;
             this.long2 = long2;
         }

         @Override
        public int hashCode() {
            return (int) ((long1 + 17) * 37 + long2 + 17);
        }

         @Override
         public boolean equals(Object obj) {
             if (obj == null) {
                 return false;
             }
             if (getClass() != obj.getClass()) {
                 return false;
             }
             final SomeClass.HashEntry other = (SomeClass.HashEntry) obj;
             if (this.long1 != other.long1) {
                 return false;
             }
             if (this.long2 != other.long2) {
                 return false;
             }
             return true;
         }
    }

    public void addToChache( long a, long b, String value ) {
        hashTable.put( new HashEntry(a, b), value );
    }
}