Java Reference
In-Depth Information
✓
✓
6.14
True or false? When an array is passed to a method, a new array is created and passed
to the method.
Check
Point
6.15
Show the output of the following two programs:
public class
Test {
public static void
main(String[] args) {
int
number =
0
;
int
[] numbers =
new int
[
1
];
public class
Test {
public static void
main(String[] args) {
int
[] list = {
1
,
2
,
3
,
4
,
5
};
reverse(list);
for
(
int
i =
0
; i < list.length; i++)
System.out.print(list[i] +
" "
);
m(number, numbers);
}
System.out.println(
"number is "
+ number
+
" and numbers[0] is "
+ numbers[
0
]);
public static void
reverse(
int
[] list) {
int
[] newList =
new int
[list.length];
}
public static void
m(
int
x,
int
[] y) {
x =
3
;
y[
0
] =
3
;
for
(
int
i =
0
; i < list.length; i++)
newList[i] = list[list.length -
1
- i];
}
list = newList;
}
}
}
(a)
(b)
6.16
Where are the arrays stored during execution? Show the contents of the stack and
heap during and after executing
displayArray
,
countLetters
,
displayCounts
in Listing 6.4.
A variable number of arguments of the same type can be passed to a method and
treated as an array.
Key
Point
You can pass a variable number of arguments of the same type to a method. The parameter in
the method is declared as follows:
typeName... parameterName
In the method declaration, you specify the type followed by an ellipsis (
...
). Only one
variable-length parameter may be specified in a method, and this parameter must be the last
parameter. Any regular parameters must precede it.
Java treats a variable-length parameter as an array. You can pass an array or a variable
number of arguments to a variable-length parameter. When invoking a method with a variable
number of arguments, Java creates an array and passes the arguments to it. Listing 6.5 con-
tains a method that prints the maximum value in a list of an unspecified number of values.
L
ISTING
6.5
VarArgsDemo.java
1
public class
VarArgsDemo {
2
public static void
main(String[] args) {
pass variable-length arg list
pass an array arg
3
4
5 }
6
7
printMax(
34
,
3
,
3
,
2
,
56
.
5
);
printMax(
new double
[]{
1
,
2
,
3
});
a variable-length arg
parameter
public static void
printMax(
double
... numbers
) {
8
if
(numbers.length ==
0
) {
9 System.out.println(
"No argument passed"
);
