Being able to write your own equals/hashCode for a custom class seems appealing - see Non-primitive Types in Map Keys and Sets. But with no hashCode method exposed in Apex string or decimal or any of the other primitive types, building a correct and efficient hashCode for a custom class that has a few fields of different types looks way harder than it should be.


  • 1
    Yes most interesting, wondering why the only sample is using numbers as an example? ;-) Looks like there is a bug in this area at large anyway, success.salesforce.com/issues_view?id=a1p30000000SV0XAAW – Andrew Fawcett Nov 19 '12 at 23:17
  • Good gawd, that bug makes the entire feature unusable if it's really that simple a repro. Even if it wasn't there, Keith is right, not exposing hashCode in the primitives makes it more painful to roll your own. Until that happens, best bet is to create a set of primitive hash utility methods that copy the logic from Java or .NET. Still the point is moot until they fix maps and sets. – jkraybill Nov 20 '12 at 1:11
  • On na14 these pass: – Keith C Nov 20 '12 at 9:33
  • I saw the bug report but couldn't reproduce. What I see is that these pass on na14 but not on na3 system.assertEquals(1, numberSet.size()) system.assertEquals(1, numberMap.size()) and this fails on both system.assertEquals(t1, t2). A new low has been reached here. – Keith C Nov 20 '12 at 9:43
  • Salesforce broke your link so hard. Here is a newer version. – Adrian Larson Jul 27 '15 at 15:58

Summer'13 Update:

According to the Summer'13 release notes String now provides a hashCode method! Here is the sample code included in the release notes here.

public class MyCustomClass {
    String x,y;
    public MyCustomClass(String a, String b) {
    public Integer hashCode() {
        return (31 * x.hashCode()) ^ y.hashCode();
    public Boolean equals(Object obj) {
        if (obj instanceof MyCustomClass) {
            MyCustomClass p = (MyCustomClass)obj;
            return (x.equals(p.x)) && (y.equals(p.y));
        return false;

Original Answer:

Converted comment to an answer after a bit of digging around.

Initial thoughts...

Yes most interesting, I did wonder why the only sample was using numbers. It also looks like there is a bug in this area at large anyway, http://success.salesforce.com/issues_view?id=a1p30000000SV0XAAW.

Current conclusion...

I had a look at the Java implementations and a few other general postings on the net. My conclusion is that given the statement governor, at least for strings, it is going to quite expensive to implement a String.hashCode. We really need a native implementation of this to avoid hitting the statement governor very quickly with large maps.

Some interesting links

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  • Could an MD5 hash generated using the Crypto class be used as a substitute? – techtrekker Nov 20 '12 at 10:06
  • Have just been trawling the Apex docs and came across that, the trick is going to be turning this into an Integer to return from the hashCode method. – Andrew Fawcett Nov 20 '12 at 10:14
  • It shouldnt matter right, if the string (blobs) are 'equal', the resulting hashes should be the same ? – techtrekker Nov 20 '12 at 11:06
  • I'm just not sure how both equals and hashCode could be implemented this way though? (putting aside its a big hammer for a large nut of course) How would the hashCode method be implemented? – Andrew Fawcett Nov 20 '12 at 11:15
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    Posted Expose hashCode on all Apex primitives so hashCode viable for custom classes in the IdeaExchange to at least publicise that particular problem a bit more. – Keith C Nov 21 '12 at 18:28

I realize Summer '13 is just around the corner, but if you are still looking for a way to create a hashcode out of strings (or any other object) without hitting governor limits, here is a method I pieced together using the solution found here

private static final Long prime = 524287L;
public static Integer getHashCode(Object obj) {
    String objHex = null;
    if(obj instanceof Id) {
        objHex = EncodingUtil.convertToHex(Blob.valueOf((String)obj));
    } else if(obj != null) {
        Blob objJSONBlob = Blob.valueOf(JSON.serialize(obj));
        Blob objHMAC = Crypto.generateMac('hmacSHA1', objJSONBlob, Blob.valueOf('a key that does not matter'));
        objHex = EncodingUtil.convertToHex(objHMAC);
    if(objHex != null) {
        Long hash = 0L;
        for(String sChar : objHex.split('')){
            if(String.isEmpty(sChar)) {
            hash = ((hash ^ hexToInteger.get(sChar)) * prime);
        return (Integer)hash;
    } else {
        return 0;
| improve this answer | |

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