Java Reference
In-Depth Information
For instance, the following statement in (a) can be simplified as in (b) due to autoboxing.
Equivalent
Integer intObject =
2
;
Integer intObject =
new
Integer(
2
);
(b)
(a)
autoboxing
Consider the following example:
1 Integer[] intArray = {
1
,
2
,
3
};
2 System.out.println(intArray[
0
] + intArray[
1
] + intArray[
2
]);
In line 1, the primitive values
1
,
2
, and
3
are automatically boxed into objects
new Inte-
ger(1)
,
new Integer(2)
, and
new Integer(3)
. In line 2, the objects
intArray[0]
,
intArray[1]
, and
intArray[2]
are automatically converted into
int
values that are
added together.
10.19
What are autoboxing and autounboxing? Are the following statements correct?
✓
✓
Check
Point
a.
Integer x =
3
+
new
Integer(
5
);
b.
Integer x =
3
;
c.
Double x =
3
;
d.
Double x =
3.0
;
e.
int
x =
new
Integer(
3
);
f.
int
x =
new
Integer(
3
) +
new
Integer(
4
);
10.20
Show the output of the following code?
public class
Test {
public static void
main(String[] args) {
Double x =
new
Double(
3.5
);
System.out.println(x.intValue());
System.out.println(x.compareTo(
4.5
));
}
}
The
BigInteger
and
BigDecimal
classes can be used to represent integers or
decimal numbers of any size and precision.
Key
Point
If you need to compute with very large integers or high-precision floating-point values, you can
use the
BigInteger
and
BigDecimal
classes in the
java.math
package. Both are
immutable
.
The largest integer of the
long
type is
Long.MAX_VALUE
(i.e.,
9223372036854775807
).
An instance of
BigInteger
can represent an integer of any size. You can use
new BigInte-
ger(String)
and
new BigDecimal(String)
to create an instance of
BigInteger
and
BigDecimal
, use the
add
,
subtract
,
multiple
,
divide
, and
remainder
methods to per-
form arithmetic operations, and use the
compareTo
method to compare two big numbers. For
example, the following code creates two
BigInteger
objects and multiplies them.
VideoNote
Process large numbers
immutable
BigInteger a =
new
BigInteger(
"9223372036854775807"
);
BigInteger b =
new
BigInteger(
"2"
);
BigInteger c = a.multiply(b);
// 9223372036854775807 * 2
System.out.println(c);
The output is
18446744073709551614
.
