java.awt.image
Class ComponentSampleModel

java.lang.Object
  java.awt.image.SampleModel
      java.awt.image.ComponentSampleModel

Direct Known Subclasses:

BandedSampleModel, PixelInterleavedSampleModel

public class ComponentSampleModel

extends SampleModel

This class represents image data which is stored such that each sample of a pixel occupies one data element of the DataBuffer. It stores the N samples which make up a pixel in N separate data array elements. Different bands may be in different banks of the DataBuffer. Accessor methods are provided so that image data can be manipulated directly. This class can support different kinds of interleaving, e.g. band interleaving, scanline interleaving, and pixel interleaving. Pixel stride is the number of data array elements between two samples for the same band on the same scanline. Scanline stride is the number of data array elements between a given sample and the corresponding sample in the same column of the next scanline. Band offsets denote the number of data array elements from the first data array element of the bank of the DataBuffer holding each band to the first sample of the band. The bands are numbered from 0 to N-1. This class can represent image data for which each sample is an unsigned integral number which can be stored in 8, 16, or 32 bits (using DataBuffer.TYPE_BYTE, DataBuffer.TYPE_USHORT, or DataBuffer.TYPE_INT, respectively), data for which each sample is a signed integral number which can be stored in 16 bits (using DataBuffer.TYPE_SHORT), or data for which each sample is a signed float or double quantity (using DataBuffer.TYPE_FLOAT or DataBuffer.TYPE_DOUBLE, respectively). All samples of a given ComponentSampleModel are stored with the same precision. All strides and offsets must be non-negative. This class supports TYPE_BYTE, TYPE_USHORT, TYPE_SHORT, TYPE_INT, TYPE_FLOAT, TYPE_DOUBLE,

See Also:

PixelInterleavedSampleModel, BandedSampleModel

Field Summary

protected int[]	bandOffsets Offsets for all bands in data array elements.
protected int[]	bankIndices Index for each bank storing a band of image data.
protected int	numBands The number of bands in this ComponentSampleModel.
protected int	numBanks The number of banks in this ComponentSampleModel.
protected int	pixelStride Pixel stride (in data array elements) of the region of image data described by this ComponentSampleModel.
protected int	scanlineStride Line stride (in data array elements) of the region of image data described by this ComponentSampleModel.

Fields inherited from class java.awt.image.SampleModel

dataType, height, width

Constructor Summary

ComponentSampleModel(int dataType, int w, int h, int pixelStride, int scanlineStride, int[] bandOffsets)
Constructs a ComponentSampleModel with the specified parameters.

ComponentSampleModel(int dataType, int w, int h, int pixelStride, int scanlineStride, int[] bankIndices, int[] bandOffsets)
Constructs a ComponentSampleModel with the specified parameters.

Method Summary

SampleModel	createCompatibleSampleModel(int w, int h) Creates a new ComponentSampleModel with the specified width and height.
DataBuffer	createDataBuffer() Creates a DataBuffer that corresponds to this ComponentSampleModel.
SampleModel	createSubsetSampleModel(int[] bands) Creates a new ComponentSampleModel with a subset of the bands of this ComponentSampleModel.
boolean	equals(Object o) Indicates whether some other object is "equal to" this one.
int[]	getBandOffsets() Returns the band offset for all bands.
int[]	getBankIndices() Returns the bank indices for all bands.
private long	getBufferSize() Returns the size of the data buffer (in data elements) needed for a data buffer that matches this ComponentSampleModel.
Object	getDataElements(int x, int y, Object obj, DataBuffer data) Returns data for a single pixel in a primitive array of type TransferType.
int	getNumDataElements() Returns the number of data elements needed to transfer a pixel with the getDataElements(int, int, Object, DataBuffer) and setDataElements(int, int, Object, DataBuffer) methods.
int	getOffset(int x, int y) Gets the offset for the first band of pixel (x,y).
int	getOffset(int x, int y, int b) Gets the offset for band b of pixel (x,y).
int[]	getPixel(int x, int y, int[] iArray, DataBuffer data) Returns all samples for the specified pixel in an int array, one sample per array element.
int[]	getPixels(int x, int y, int w, int h, int[] iArray, DataBuffer data) Returns all samples for the specified rectangle of pixels in an int array, one sample per array element.
int	getPixelStride() Returns the pixel stride of this ComponentSampleModel.
int	getSample(int x, int y, int b, DataBuffer data) Returns as int the sample in a specified band for the pixel located at (x,y).
double	getSampleDouble(int x, int y, int b, DataBuffer data) Returns the sample in a specified band for a pixel located at (x,y) as a double.
float	getSampleFloat(int x, int y, int b, DataBuffer data) Returns the sample in a specified band for the pixel located at (x,y) as a float.
int[]	getSamples(int x, int y, int w, int h, int b, int[] iArray, DataBuffer data) Returns the samples in a specified band for the specified rectangle of pixels in an int array, one sample per data array element.
int[]	getSampleSize() Returns the number of bits per sample for all bands.
int	getSampleSize(int band) Returns the number of bits per sample for the specified band.
int	getScanlineStride() Returns the scanline stride of this ComponentSampleModel.
int	hashCode() Returns a hash code value for the object.
private static void	initIDs()
(package private) int[]	orderBands(int[] orig, int step) Preserves band ordering with new step factor...
void	setDataElements(int x, int y, Object obj, DataBuffer data) Sets the data for a single pixel in the specified DataBuffer from a primitive array of type TransferType.
void	setPixel(int x, int y, int[] iArray, DataBuffer data) Sets a pixel in the DataBuffer using an int array of samples for input.
void	setPixels(int x, int y, int w, int h, int[] iArray, DataBuffer data) Sets all samples for a rectangle of pixels from an int array containing one sample per array element.
void	setSample(int x, int y, int b, double s, DataBuffer data) Sets a sample in the specified band for the pixel located at (x,y) in the DataBuffer using a double for input.
void	setSample(int x, int y, int b, float s, DataBuffer data) Sets a sample in the specified band for the pixel located at (x,y) in the DataBuffer using a float for input.
void	setSample(int x, int y, int b, int s, DataBuffer data) Sets a sample in the specified band for the pixel located at (x,y) in the DataBuffer using an int for input.
void	setSamples(int x, int y, int w, int h, int b, int[] iArray, DataBuffer data) Sets the samples in the specified band for the specified rectangle of pixels from an int array containing one sample per data array element.

Methods inherited from class java.awt.image.SampleModel

getDataElements, getDataType, getHeight, getNumBands, getPixel, getPixel, getPixels, getPixels, getSamples, getSamples, getTransferType, getWidth, setDataElements, setPixel, setPixel, setPixels, setPixels, setSamples, setSamples

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Field Detail

bandOffsets

protected int[] bandOffsets

Offsets for all bands in data array elements.

bankIndices

protected int[] bankIndices

Index for each bank storing a band of image data.

numBands

protected int numBands

The number of bands in this ComponentSampleModel.

numBanks

protected int numBanks

The number of banks in this ComponentSampleModel.

scanlineStride

protected int scanlineStride

Line stride (in data array elements) of the region of image data described by this ComponentSampleModel.

pixelStride

protected int pixelStride

Pixel stride (in data array elements) of the region of image data described by this ComponentSampleModel.

Constructor Detail

ComponentSampleModel

public ComponentSampleModel(int dataType,
                            int w,
                            int h,
                            int pixelStride,
                            int scanlineStride,
                            int[] bandOffsets)

Constructs a ComponentSampleModel with the specified parameters. The number of bands will be given by the length of the bandOffsets array. All bands will be stored in the first bank of the DataBuffer.

Parameters:

dataType - the data type for storing samples

w - the width (in pixels) of the region of image data described

h - the height (in pixels) of the region of image data described

pixelStride - the pixel stride of the region of image data described

scanlineStride - the line stride of the region of image data described

bandOffsets - the offsets of all bands

Throws:

IllegalArgumentException - if w or h is not greater than 0

IllegalArgumentException - if pixelStride is less than 0

IllegalArgumentException - if scanlineStride is less than 0

IllegalArgumentException - if numBands is less than 1

IllegalArgumentException - if the product of w and h is greater than Integer.MAX_VALUE

IllegalArgumentException - if dataType is not one of the supported data types

ComponentSampleModel

public ComponentSampleModel(int dataType,
                            int w,
                            int h,
                            int pixelStride,
                            int scanlineStride,
                            int[] bankIndices,
                            int[] bandOffsets)

Constructs a ComponentSampleModel with the specified parameters. The number of bands will be given by the length of the bandOffsets array. Different bands may be stored in different banks of the DataBuffer.

Parameters:

dataType - the data type for storing samples

w - the width (in pixels) of the region of image data described

h - the height (in pixels) of the region of image data described

pixelStride - the pixel stride of the region of image data described

scanlineStride - The line stride of the region of image data described

bankIndices - the bank indices of all bands

bandOffsets - the band offsets of all bands

Throws:

IllegalArgumentException - if w or h is not greater than 0

IllegalArgumentException - if pixelStride is less than 0

IllegalArgumentException - if scanlineStride is less than 0

IllegalArgumentException - if the length of bankIndices does not equal the length of bankOffsets

IllegalArgumentException - if any of the bank indices of bandIndices is less than 0

IllegalArgumentException - if dataType is not one of the supported data types

Method Detail

initIDs

private static void initIDs()

getBufferSize

private long getBufferSize()

Returns the size of the data buffer (in data elements) needed for a data buffer that matches this ComponentSampleModel.

orderBands

int[] orderBands(int[] orig,
                 int step)

Preserves band ordering with new step factor...

createCompatibleSampleModel

public SampleModel createCompatibleSampleModel(int w,
                                               int h)

Creates a new ComponentSampleModel with the specified width and height. The new SampleModel will have the same number of bands, storage data type, interleaving scheme, and pixel stride as this SampleModel.

Specified by:

createCompatibleSampleModel in class SampleModel

Parameters:

w - the width of the resulting SampleModel

h - the height of the resulting SampleModel

Returns:

a new ComponentSampleModel with the specified size

Throws:

IllegalArgumentException - if w or h is not greater than 0

createSubsetSampleModel

public SampleModel createSubsetSampleModel(int[] bands)

Creates a new ComponentSampleModel with a subset of the bands of this ComponentSampleModel. The new ComponentSampleModel can be used with any DataBuffer that the existing ComponentSampleModel can be used with. The new ComponentSampleModel/DataBuffer combination will represent an image with a subset of the bands of the original ComponentSampleModel/DataBuffer combination.

Specified by:

createSubsetSampleModel in class SampleModel

Parameters:

bands - a subset of bands from this ComponentSampleModel

Returns:

a ComponentSampleModel created with a subset of bands from this ComponentSampleModel.

createDataBuffer

public DataBuffer createDataBuffer()

Creates a DataBuffer that corresponds to this ComponentSampleModel. The DataBuffer object's data type, number of banks, and size are be consistent with this ComponentSampleModel.

Specified by:

createDataBuffer in class SampleModel

Returns:

a DataBuffer whose data type, number of banks and size are consistent with this ComponentSampleModel.

getOffset

public int getOffset(int x,
                     int y)

Gets the offset for the first band of pixel (x,y). A sample of the first band can be retrieved from a DataBuffer data with a ComponentSampleModel csm as

        data.getElem(csm.getOffset(x, y));
 

Returns:

the offset for the first band of the specified pixel.

getOffset

public int getOffset(int x,
                     int y,
                     int b)

Gets the offset for band b of pixel (x,y). A sample of band b can be retrieved from a DataBuffer data with a ComponentSampleModel csm as

       data.getElem(csm.getOffset(x, y, b));
 

Parameters:

b - the specified band

Returns:

the offset for the specified band of the specified pixel.

getSampleSize

public final int[] getSampleSize()

Returns the number of bits per sample for all bands.

Specified by:

getSampleSize in class SampleModel

Returns:

an array containing the number of bits per sample for all bands, where each element in the array represents a band.

getSampleSize

public final int getSampleSize(int band)

Returns the number of bits per sample for the specified band.

Specified by:

getSampleSize in class SampleModel

Parameters:

band - the specified band

Returns:

the number of bits per sample for the specified band.

getBankIndices

public final int[] getBankIndices()

Returns the bank indices for all bands.

Returns:

the bank indices for all bands.

getBandOffsets

public final int[] getBandOffsets()

Returns the band offset for all bands.

Returns:

the band offsets for all bands.

getScanlineStride

public final int getScanlineStride()

Returns the scanline stride of this ComponentSampleModel.

Returns:

the scanline stride of this ComponentSampleModel.

getPixelStride

public final int getPixelStride()

Returns the pixel stride of this ComponentSampleModel.

Returns:

the pixel stride of this ComponentSampleModel.

getNumDataElements

public final int getNumDataElements()

Returns the number of data elements needed to transfer a pixel with the getDataElements(int, int, Object, DataBuffer) and setDataElements(int, int, Object, DataBuffer) methods. For a ComponentSampleModel, this is identical to the number of bands.

Specified by:

getNumDataElements in class SampleModel

Returns:

the number of data elements needed to transfer a pixel with the getDataElements and setDataElements methods.

See Also:

SampleModel.getNumDataElements(), SampleModel.getNumBands()

getDataElements

public Object getDataElements(int x,
                              int y,
                              Object obj,
                              DataBuffer data)

Returns data for a single pixel in a primitive array of type TransferType. For a ComponentSampleModel, this is the same as the data type, and samples are returned one per array element. Generally, obj should be passed in as null, so that the Object is created automatically and is the right primitive data type.

The following code illustrates transferring data for one pixel from DataBuffer db1, whose storage layout is described by ComponentSampleModel csm1, to DataBuffer db2, whose storage layout is described by ComponentSampleModel csm2. The transfer is usually more efficient than using getPixel and setPixel.

 	     ComponentSampleModel csm1, csm2;
	     DataBufferInt db1, db2;
 	     csm2.setDataElements(x, y,
                            csm1.getDataElements(x, y, null, db1), db2);
 

Using getDataElements and setDataElements to transfer between two DataBuffer/SampleModel pairs is legitimate if the SampleModel objects have the same number of bands, corresponding bands have the same number of bits per sample, and the TransferTypes are the same.

If obj is not null, it should be a primitive array of type TransferType. Otherwise, a ClassCastException is thrown. An ArrayIndexOutOfBoundsException might be thrown if the coordinates are not in bounds, or if obj is not null and is not large enough to hold the pixel data.

Specified by:

getDataElements in class SampleModel

Parameters:

obj - if non-null, a primitive array in which to return the pixel data

data - the DataBuffer containing the image data

x - The X coordinate of the pixel location.

y - The Y coordinate of the pixel location.

Returns:

the data of the specified pixel

Throws:

NullPointerException - if data is null.

ArrayIndexOutOfBoundsException - if the coordinates are not in bounds, or if obj is too small to hold the ouput.

See Also:

setDataElements(int, int, Object, DataBuffer)

getPixel

public int[] getPixel(int x,
                      int y,
                      int[] iArray,
                      DataBuffer data)

Returns all samples for the specified pixel in an int array, one sample per array element. An ArrayIndexOutOfBoundsException might be thrown if the coordinates are not in bounds.

Overrides:

getPixel in class SampleModel

Parameters:

iArray - If non-null, returns the samples in this array

data - The DataBuffer containing the image data

Returns:

the samples of the specified pixel.

Throws:

NullPointerException - if data is null.

ArrayIndexOutOfBoundsException - if the coordinates are not in bounds, or if iArray is too small to hold the output.

See Also:

setPixel(int, int, int[], DataBuffer)

getPixels

public int[] getPixels(int x,
                       int y,
                       int w,
                       int h,
                       int[] iArray,
                       DataBuffer data)

Returns all samples for the specified rectangle of pixels in an int array, one sample per array element. An ArrayIndexOutOfBoundsException might be thrown if the coordinates are not in bounds.

Overrides:

getPixels in class SampleModel

Parameters:

w - The width of the pixel rectangle

h - The height of the pixel rectangle

iArray - If non-null, returns the samples in this array

data - The DataBuffer containing the image data

x - The X coordinate of the upper left pixel location.

y - The Y coordinate of the upper left pixel location.

Returns:

the samples of the pixels within the specified region.

See Also:

setPixels(int, int, int, int, int[], DataBuffer)

getSample

public int getSample(int x,
                     int y,
                     int b,
                     DataBuffer data)

Returns as int the sample in a specified band for the pixel located at (x,y). An ArrayIndexOutOfBoundsException might be thrown if the coordinates are not in bounds.

Specified by:

getSample in class SampleModel

Parameters:

b - the band to return

data - the DataBuffer containing the image data

x - The X coordinate of the pixel location.

y - The Y coordinate of the pixel location.

Returns:

the sample in a specified band for the specified pixel

See Also:

setSample(int, int, int, int, DataBuffer)

getSampleFloat

public float getSampleFloat(int x,
                            int y,
                            int b,
                            DataBuffer data)

Returns the sample in a specified band for the pixel located at (x,y) as a float. An ArrayIndexOutOfBoundsException might be thrown if the coordinates are not in bounds.

Overrides:

getSampleFloat in class SampleModel

Parameters:

b - The band to return

data - The DataBuffer containing the image data

x - The X coordinate of the pixel location.

y - The Y coordinate of the pixel location.

Returns:

a float value representing the sample in the specified band for the specified pixel.

getSampleDouble

public double getSampleDouble(int x,
                              int y,
                              int b,
                              DataBuffer data)

Returns the sample in a specified band for a pixel located at (x,y) as a double. An ArrayIndexOutOfBoundsException might be thrown if the coordinates are not in bounds.

Overrides:

getSampleDouble in class SampleModel

Parameters:

b - The band to return

data - The DataBuffer containing the image data

x - The X coordinate of the pixel location.

y - The Y coordinate of the pixel location.

Returns:

a double value representing the sample in the specified band for the specified pixel.

getSamples

public int[] getSamples(int x,
                        int y,
                        int w,
                        int h,
                        int b,
                        int[] iArray,
                        DataBuffer data)

Returns the samples in a specified band for the specified rectangle of pixels in an int array, one sample per data array element. An ArrayIndexOutOfBoundsException might be thrown if the coordinates are not in bounds.

Overrides:

getSamples in class SampleModel

Parameters:

w - the width of the pixel rectangle

h - the height of the pixel rectangle

b - the band to return

iArray - if non-null, returns the samples in this array

data - the DataBuffer containing the image data

x - The X coordinate of the upper left pixel location.

y - The Y coordinate of the upper left pixel location.

Returns:

the samples in the specified band of the specified pixel

See Also:

setSamples(int, int, int, int, int, int[], DataBuffer)

setDataElements

public void setDataElements(int x,
                            int y,
                            Object obj,
                            DataBuffer data)

Sets the data for a single pixel in the specified DataBuffer from a primitive array of type TransferType. For a ComponentSampleModel, this is the same as the data type, and samples are transferred one per array element.

The following code illustrates transferring data for one pixel from DataBuffer db1, whose storage layout is described by ComponentSampleModel csm1, to DataBuffer db2, whose storage layout is described by ComponentSampleModel csm2. The transfer is usually more efficient than using getPixel and setPixel.

 	     ComponentSampleModel csm1, csm2;
	     DataBufferInt db1, db2;
 	     csm2.setDataElements(x, y, csm1.getDataElements(x, y, null, db1),
                            db2);
 

Using getDataElements and setDataElements to transfer between two DataBuffer/SampleModel pairs is legitimate if the SampleModel objects have the same number of bands, corresponding bands have the same number of bits per sample, and the TransferTypes are the same.

A ClassCastException is thrown if obj is not a primitive array of type TransferType. An ArrayIndexOutOfBoundsException might be thrown if the coordinates are not in bounds, or if obj is not large enough to hold the pixel data.

Specified by:

setDataElements in class SampleModel

Parameters:

obj - a primitive array containing pixel data

data - the DataBuffer containing the image data

x - The X coordinate of the pixel location.

y - The Y coordinate of the pixel location.

See Also:

getDataElements(int, int, Object, DataBuffer)

setPixel

public void setPixel(int x,
                     int y,
                     int[] iArray,
                     DataBuffer data)

Sets a pixel in the DataBuffer using an int array of samples for input. An ArrayIndexOutOfBoundsException might be thrown if the coordinates are not in bounds.

Overrides:

setPixel in class SampleModel

Parameters:

iArray - The input samples in an int array

data - The DataBuffer containing the image data

x - The X coordinate of the pixel location.

y - The Y coordinate of the pixel location.

See Also:

getPixel(int, int, int[], DataBuffer)

setPixels

public void setPixels(int x,
                      int y,
                      int w,
                      int h,
                      int[] iArray,
                      DataBuffer data)

Sets all samples for a rectangle of pixels from an int array containing one sample per array element. An ArrayIndexOutOfBoundsException might be thrown if the coordinates are not in bounds.

Overrides:

setPixels in class SampleModel

Parameters:

w - The width of the pixel rectangle

h - The height of the pixel rectangle

iArray - The input samples in an int array

data - The DataBuffer containing the image data

x - The X coordinate of the upper left pixel location.

y - The Y coordinate of the upper left pixel location.

See Also:

getPixels(int, int, int, int, int[], DataBuffer)

setSample

public void setSample(int x,
                      int y,
                      int b,
                      int s,
                      DataBuffer data)

Sets a sample in the specified band for the pixel located at (x,y) in the DataBuffer using an int for input. An ArrayIndexOutOfBoundsException might be thrown if the coordinates are not in bounds.

Specified by:

setSample in class SampleModel

Parameters:

b - the band to set

s - the input sample as an int

data - the DataBuffer containing the image data

x - The X coordinate of the pixel location.

y - The Y coordinate of the pixel location.

See Also:

getSample(int, int, int, DataBuffer)

setSample

public void setSample(int x,
                      int y,
                      int b,
                      float s,
                      DataBuffer data)

Sets a sample in the specified band for the pixel located at (x,y) in the DataBuffer using a float for input. An ArrayIndexOutOfBoundsException might be thrown if the coordinates are not in bounds.

Overrides:

setSample in class SampleModel

Parameters:

b - The band to set

s - The input sample as a float

data - The DataBuffer containing the image data

x - The X coordinate of the pixel location.

y - The Y coordinate of the pixel location.

See Also:

getSample(int, int, int, DataBuffer)

setSample

public void setSample(int x,
                      int y,
                      int b,
                      double s,
                      DataBuffer data)

Sets a sample in the specified band for the pixel located at (x,y) in the DataBuffer using a double for input. An ArrayIndexOutOfBoundsException might be thrown if the coordinates are not in bounds.

Overrides:

setSample in class SampleModel

Parameters:

b - The band to set

s - The input sample as a double

data - The DataBuffer containing the image data

x - The X coordinate of the pixel location.

y - The Y coordinate of the pixel location.

See Also:

getSample(int, int, int, DataBuffer)

setSamples

public void setSamples(int x,
                       int y,
                       int w,
                       int h,
                       int b,
                       int[] iArray,
                       DataBuffer data)

Sets the samples in the specified band for the specified rectangle of pixels from an int array containing one sample per data array element. An ArrayIndexOutOfBoundsException might be thrown if the coordinates are not in bounds.

Overrides:

setSamples in class SampleModel

Parameters:

w - The width of the pixel rectangle

h - The height of the pixel rectangle

b - The band to set

iArray - The input samples in an int array

data - The DataBuffer containing the image data

x - The X coordinate of the upper left pixel location.

y - The Y coordinate of the upper left pixel location.

See Also:

getSamples(int, int, int, int, int, int[], DataBuffer)

equals

public boolean equals(Object o)

Description copied from class: Object

Indicates whether some other object is "equal to" this one.

The equals method implements an equivalence relation on non-null object references:

• It is reflexive: for any non-null reference value x, x.equals(x) should return true.
• It is symmetric: for any non-null reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true.
• It is transitive: for any non-null reference values x, y, and z, if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true.
• It is consistent: for any non-null reference values x and y, multiple invocations of x.equals(y) consistently return true or consistently return false, provided no information used in equals comparisons on the objects is modified.
• For any non-null reference value x, x.equals(null) should return false.

The equals method for class Object implements the most discriminating possible equivalence relation on objects; that is, for any non-null reference values x and y, this method returns true if and only if x and y refer to the same object (x == y has the value true).

Note that it is generally necessary to override the hashCode method whenever this method is overridden, so as to maintain the general contract for the hashCode method, which states that equal objects must have equal hash codes.

Overrides:

equals in class Object

Parameters:

o - the reference object with which to compare.

Returns:

true if this object is the same as the obj argument; false otherwise.

See Also:

Object.hashCode(), Hashtable

hashCode

public int hashCode()

Description copied from class: Object

Returns a hash code value for the object. This method is supported for the benefit of hashtables such as those provided by java.util.Hashtable.

The general contract of hashCode is:

• Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer, provided no information used in equals comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application.
• If two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result.
• It is not required that if two objects are unequal according to the Object.equals(java.lang.Object) method, then calling the hashCode method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hashtables.

As much as is reasonably practical, the hashCode method defined by class Object does return distinct integers for distinct objects. (This is typically implemented by converting the internal address of the object into an integer, but this implementation technique is not required by the Java^TM programming language.)

Overrides:

hashCode in class Object

Returns:

a hash code value for this object.

See Also:

Object.equals(java.lang.Object), Hashtable