How to compare two java objects [duplicate]

Question

I have two java objects that are instantiated from the same class.

MyClass myClass1 = new MyClass(); MyClass myClass2 = new MyClass(); 

If I set both of their properties to the exact same values and then verify that they are the same

if(myClass1 == myClass2){    // objects match    ...  }  if(myClass1.equals(myClass2)){    // objects match    ...  } 

However, neither of these approaches return a true value. I have checked the properties of each and they match.

How do I compare these two objects to verify that they are identical?

Answer 1

You need to provide your own implementation of equals() in MyClass.

@Override public boolean equals(Object other) {     if (!(other instanceof MyClass)) {         return false;     }      MyClass that = (MyClass) other;      // Custom equality check here.     return this.field1.equals(that.field1)         && this.field2.equals(that.field2); } 

You should also override hashCode() if there's any chance of your objects being used in a hash table. A reasonable implementation would be to combine the hash codes of the object's fields with something like:

@Override public int hashCode() {     int hashCode = 1;      hashCode = hashCode * 37 + this.field1.hashCode();     hashCode = hashCode * 37 + this.field2.hashCode();      return hashCode; } 

See this question for more details on implementing a hash function.