Does ArrayList's `contains()` Method Compare Object References or Values?

How ArrayList's contains() Method Determines Object Equality

Question:

Consider an ArrayList containing an object named 'thing' constructed with the integer 100. If a second object named 'another' is created with the same constructor input, will ArrayList's contains() method evaluate 'thing' and 'another' as equal?

Answer:

ArrayList's contains() method relies on the equals() method to determine object equality. By default, this method compares object references rather than their content.

In the provided code snippet, the Thing class overrides the equals() method to compare the value field. So, the contains() method will return true if 'thing' and 'another' have the same value, regardless of whether they are the same object references.

Implementation for Equality Check:

Yes, the provided implementation of the Thing class, which overrides the equals() method based on the value, will make contains() return true for objects with identical values. Overriding equals() is necessary to compare the content (value field) instead of object references.

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