Java HashMap.containsKey() doesn't call equals()

Question

I have a hashmap:

Map<LotWaferBean, File> hm = new HashMap<LotWaferBean, File>();  LotWaferBean lw = new LotWaferBean(); ... //populate lw if (!hm.containsKey((LotWaferBean) lw)) {   hm.put(lw, triggerFiles[l]); } 

The code for LotWaferBean:

@Override public boolean equals(Object o) {         if (!(o instanceof LotWaferBean)) {               return false;         }         if (((LotWaferBean) o).getLotId().equals(lotId)                     && ((LotWaferBean) o).getWaferNo() == waferNo) {               return true;         }         return false;   } 

In my IDE I put breakpoints in equals() but it is never executed. Why?

Answer 1

Try putting a breakpoint in hashCode().

If the hashCode() of two objects in a map return the same number, then equals will be called to determine if they're really equal.

Answer 2

JVM checks the hashcode bucket of that object's hashcode, if there are more objects with the same hashcode, then only, the equals() method will be executed. And, the developer should follow correct contract between the hashCode() and equals() methods.