René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"JSONObject#equals method violates the contract of equals","articleBody":"The `equals` method of `JSONObject#Null` violates the [“non-nullity”](http://books.google.com/books?id=ka2VUBqHiWkC\u0026pg=PA41) requirement of the equals method in Java. Since `null` in Java is not an Object, and does not provide an equals method, `null.equals( JSONObject.NULL )` cannot return `true` while `JSONObject.NULL.equals( null )` does so. Hence, this equals implementation is not symetric and violates the contract of an equivalence relation. No object must be equal to `null`.\n\nTools like the [equals verifier](http://code.google.com/p/equalsverifier/) fault this implementation because of this violation. Also the Java Development Tools in Eclipse complain because this class [implements equals without implementing hashCode](http://eclipsesource.com/blogs/2012/09/04/the-3-things-you-should-know-about-hashcode/).\n\nSince there is only one single instance of `JSONObject#NULL`, I'd suggest to remove the equals method from `JSONObject#Null`. `Object#equals` is a perfect fit for this class.\n","author":{"url":"https://github.com/ralfstx","@type":"Person","name":"ralfstx"},"datePublished":"2012-09-07T09:30:43.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/65/JSON-java/issues/65"}