java.lang.Obcect A superclass of all classes. ** boolean equals (Object hoge) ** → Compare if the instances of objects are equal ** final Class <?> getClass () ** → Returns the runtime class of the object ** int hachCode () ** → Returns the hash code value of the object ** String toString () ** → Convert object to String
java.lang.Math What provides a math library.
** static final double E ** → constant e (natural logarithm constant) ** static final double PI ** → constant π (pi)
** static double random () ** → Returns a uniformly distributed random number from 0.0 to 1.0
java.time Those that handle dates and times. Introduced to eliminate deficiencies in java.util.Date (?)
Handle date with LocalDate, time with LocalTime, date + time with LocalDateTime, and period with Period.
In addition to instantiation by the current time (now) and instantiation with the time set (of), it has various functions such as conversion from a character string (parse) and date addition / subtraction (plus Days).
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