Item 10: Always override toString

java.lang.Object provides an implementation of the toString method, but it returns is generally not what the user of your class wants to see.

the returns will be followed by an ( @ ) and the unsigned hexadecimal representation of the hash code. like PhoneNumber@163b91

• We like a concise but informative representation.

It is recommended that all subclasses override this method - automatically invoked - when an object is passed to println , printf , the string concatenation operator, or assert , or printed by a debugger. - clearly document - Whether or not you decide to specify the format, you should clearly document your intentions. - programmatic access - provide programmatic access to all of the information contained in the value returned by toString.