Which of the following statements are true?

a. Override the methods equals and toString defined in the Object class whenever possible.
b. Override the hashCode method whenever the equals method is overridden. By contract, two equal objects must have the same hash code.
c. A public default no-arg constructor is assumed if no constructors are defined explicitly.
d. You should follow standard Java programming style and naming conventions. Choose informative names for classes, data fields, and methods.

abcd