Java Reference
In-Depth Information
3.
Java can automatically convert a primitive type value to its corresponding wrapper
object in the context and vice versa.
4.
The
BigInteger
class is useful for computing and processing integers of any size. The
BigDecimal
class can be used to compute and process floating-point numbers with any
arbitrary precision.
5.
A
String
object is immutable; its contents cannot be changed. To improve efficiency
and save memory, the JVM stores two literal strings that have the same character
sequence in a unique object. This unique object is called an
interned string object
.
6.
A
regular expression
(abbreviated
regex
) is a string that describes a pattern for match-
ing a set of strings. You can match, replace, or split a string by specifying a pattern.
7.
The
StringBuilder
and
StringBuffer
classes can be used to replace the
String
class. The
String
object is immutable, but you can add, insert, or append new contents
into
StringBuilder
and
StringBuffer
objects. Use
String
if the string contents
do not require any change, and use
StringBuilder
or
StringBuffer
if they might
change.
Q
UIZ
P
ROGRAMMING
E
XERCISES
Sections 10.2-10.3
*10.1
(
The
Time
class
) Design a class named
Time
. The class contains:
The data fields
hour
,
minute
, and
second
that represent a time.
■
A no-arg constructor that creates a
Time
object for the current time. (The
values of the data fields will represent the current time.)
■
A constructor that constructs a
Time
object with a specified elapsed time
since midnight, January 1, 1970, in milliseconds. (The values of the data
fields will represent this time.)
■
A constructor that constructs a
Time
object with the specified hour, minute,
and second.
■
Three getter methods for the data fields
hour
,
minute
, and
second
,
respectively.
■
A method named
setTime(long elapseTime)
that sets a new time
for the object using the elapsed time. For example, if the elapsed time is
555550000
milliseconds, the hour is
10
, the minute is
19
, and the second is
10
.
Draw the UML diagram for the class and then implement the class. Write
a test program that creates two
Time
objects (using
new Time()
and
new
Time(555550000)
) and displays their hour, minute, and second in the format
hour:minute:second.
(
Hint
: The first two constructors will extract the hour, minute, and second
from the elapsed time. For the no-arg constructor, the current time can be
obtained using
System.currentTimeMillis()
, as shown in Listing 2.7,
ShowCurrentTime.java.)
■
Search WWH ::
Custom Search