Java Reference
In-Depth Information
The letter is inserted by first shifting the contents of
packed
left by 16 bits, and then ORing the value of
letterC
with the result. At this point, the leftmost 32 bits of
packed
are zero and the rightmost 32 bits
contain
D
followed by
C
.
The next two statements repeat the same process to insert
B
and then
A
:
packed = (packed << 16) | letterB; // Shift and add the next
letter - B
packed = (packed << 16) | letterA; // Shift and add the next
letter - A
Now the variable
packed
holds the codes for all four characters in the sequence
D
,
C
,
B
, and
A
.
The output produced by the next statement confirms this:
System.out.println("packed now contains 0x" +
toHexString(packed));
This statement uses the
toHexString()
method defined in the
Long
class to generate a string containing
a hexadecimal representation of the value of
packed
. Because you have a static import statement for the
name of this method, you don't need to qualify it with the class name. You can see from the output that
this consists of the character code values
0x44
,
0x43
,
0x42
, and
0x41
, which are the codes for the letters
D
through
A
.
The program then demonstrates how you can use the shift operators combined with the bitwise AND to
extract the four
char
values from
packed
. The first step is to define a
mask
to select the rightmost 16 bits
in a value of type
long
:
long mask = 0xFFFF; // Rightmost 16 bits as 1
The next statement uses
mask
to pick out the rightmost character code in
packed
:
char letter = (char)(packed & mask); // Extract the rightmost
letter
The cast to type
char
of the value that results from ANDing
mask
with
packed
is necessary because the
compiler does not insert an automatic cast from type
long
to type
char
.
The next two statements output a heading followed by the first letter as a letter and its code:
System.out.println("From right to left the letters in packed
are:");
System.out.println(" " + letter + " 0x" + toHexString(letter));
To get at the next character, you can shift out the character just extracted and AND the result with
mask
once again:
packed >>= 16; // Shift out the
rightmost letter
letter = (char)(packed & mask); // Extract the new
rightmost letter
