public class BitField extends Object
Supports operations on bit-mapped fields. Instances of this class can be
used to store a flag or data within an int
, short
or
byte
.
Each BitField
is constructed with a mask value, which indicates
the bits that will be used to store and retrieve the data for that field.
For instance, the mask 0xFF
indicates the least-significant byte
should be used to store the data.
As an example, consider a car painting machine that accepts paint instructions as integers. Bit fields can be used to encode this:
// blue, green and red are 1 byte values (0-255) stored in the three least // significant bytes BitField blue = new BitField(0xFF); BitField green = new BitField(0xFF00); BitField red = new BitField(0xFF0000); // anyColor is a flag triggered if any color is used BitField anyColor = new BitField(0xFFFFFF); // isMetallic is a single bit flag BitField isMetallic = new BitField(0x1000000);
Using these BitField
instances, a paint instruction can be
encoded into an integer:
int paintInstruction = 0; paintInstruction = red.setValue(paintInstruction, 35); paintInstruction = green.setValue(paintInstruction, 100); paintInstruction = blue.setValue(paintInstruction, 255);
Flags and data can be retrieved from the integer:
// Prints true if red, green or blue is non-zero System.out.println(anyColor.isSet(paintInstruction)); // prints true // Prints value of red, green and blue System.out.println(red.getValue(paintInstruction)); // prints 35 System.out.println(green.getValue(paintInstruction)); // prints 100 System.out.println(blue.getValue(paintInstruction)); // prints 255 // Prints true if isMetallic was set System.out.println(isMetallic.isSet(paintInstruction)); // prints false
Constructor and Description |
---|
BitField(int mask)
Creates a BitField instance.
|
Modifier and Type | Method and Description |
---|---|
int |
clear(int holder)
Clears the bits.
|
byte |
clearByte(byte holder)
Clears the bits.
|
short |
clearShort(short holder)
Clears the bits.
|
int |
getRawValue(int holder)
Obtains the value for the specified BitField, unshifted.
|
short |
getShortRawValue(short holder)
Obtains the value for the specified BitField, unshifted.
|
short |
getShortValue(short holder)
Obtains the value for the specified BitField, appropriately
shifted right, as a short.
|
int |
getValue(int holder)
Obtains the value for the specified BitField, appropriately
shifted right.
|
boolean |
isAllSet(int holder)
Returns whether all of the bits are set or not.
|
boolean |
isSet(int holder)
Returns whether the field is set or not.
|
int |
set(int holder)
Sets the bits.
|
int |
setBoolean(int holder,
boolean flag)
Sets a boolean BitField.
|
byte |
setByte(byte holder)
Sets the bits.
|
byte |
setByteBoolean(byte holder,
boolean flag)
Sets a boolean BitField.
|
short |
setShort(short holder)
Sets the bits.
|
short |
setShortBoolean(short holder,
boolean flag)
Sets a boolean BitField.
|
short |
setShortValue(short holder,
short value)
Replaces the bits with new values.
|
int |
setValue(int holder,
int value)
Replaces the bits with new values.
|
public BitField(int mask)
Creates a BitField instance.
mask
- the mask specifying which bits apply to this
BitField. Bits that are set in this mask are the bits
that this BitField operates onpublic int getValue(int holder)
Obtains the value for the specified BitField, appropriately shifted right.
Many users of a BitField will want to treat the specified bits as an int value, and will not want to be aware that the value is stored as a BitField (and so shifted left so many bits).
holder
- the int data containing the bits we're interested
insetValue(int,int)
public short getShortValue(short holder)
Obtains the value for the specified BitField, appropriately shifted right, as a short.
Many users of a BitField will want to treat the specified bits as an int value, and will not want to be aware that the value is stored as a BitField (and so shifted left so many bits).
holder
- the short data containing the bits we're
interested insetShortValue(short,short)
public int getRawValue(int holder)
Obtains the value for the specified BitField, unshifted.
holder
- the int data containing the bits we're
interested inpublic short getShortRawValue(short holder)
Obtains the value for the specified BitField, unshifted.
holder
- the short data containing the bits we're
interested inpublic boolean isSet(int holder)
Returns whether the field is set or not.
This is most commonly used for a single-bit field, which is often used to represent a boolean value; the results of using it for a multi-bit field is to determine whether *any* of its bits are set.
holder
- the int data containing the bits we're interested
intrue
if any of the bits are set,
else false
public boolean isAllSet(int holder)
Returns whether all of the bits are set or not.
This is a stricter test than isSet(int)
,
in that all of the bits in a multi-bit set must be set
for this method to return true
.
holder
- the int data containing the bits we're
interested intrue
if all of the bits are set,
else false
public int setValue(int holder, int value)
Replaces the bits with new values.
holder
- the int data containing the bits we're
interested invalue
- the new value for the specified bitsgetValue(int)
public short setShortValue(short holder, short value)
Replaces the bits with new values.
holder
- the short data containing the bits we're
interested invalue
- the new value for the specified bitsgetShortValue(short)
public int clear(int holder)
Clears the bits.
holder
- the int data containing the bits we're
interested in0
)public short clearShort(short holder)
Clears the bits.
holder
- the short data containing the bits we're
interested in0
)public byte clearByte(byte holder)
Clears the bits.
holder
- the byte data containing the bits we're
interested in0
)public int set(int holder)
Sets the bits.
holder
- the int data containing the bits we're
interested in1
public short setShort(short holder)
Sets the bits.
holder
- the short data containing the bits we're
interested in1
public byte setByte(byte holder)
Sets the bits.
holder
- the byte data containing the bits we're
interested in1
public int setBoolean(int holder, boolean flag)
Sets a boolean BitField.
holder
- the int data containing the bits we're
interested inflag
- indicating whether to set or clear the bitspublic short setShortBoolean(short holder, boolean flag)
Sets a boolean BitField.
holder
- the short data containing the bits we're
interested inflag
- indicating whether to set or clear the bitspublic byte setByteBoolean(byte holder, boolean flag)
Sets a boolean BitField.
holder
- the byte data containing the bits we're
interested inflag
- indicating whether to set or clear the bitsCopyright © 2001–2015 The Apache Software Foundation. All rights reserved.