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## cern.colt.bitvector
Class BitMatrix

    java.lang.Object
      cern.colt.PersistentObject
          cern.colt.bitvector.BitMatrix

All Implemented Interfaces:
  Cloneable, Serializable

public class BitMatrix
extends PersistentObject

Fixed sized (non resizable) n*m bit matrix. A bit matrix has a number of columns and rows, which are assigned upon instance construction - The matrix's size is then `columns()*rows()`. Bits are accessed via `(column,row)` coordinates.

Individual bits can be examined, set, or cleared. Rectangular parts (boxes) can quickly be extracted, copied and replaced. Quick iteration over boxes is provided by optimized internal iterators (`forEach()` methods). One `BitMatrix` may be used to modify the contents of another `BitMatrix` through logical AND, OR, XOR and other similar operations.

Legal coordinates range from `[0,0]` to `[columns()-1,rows()-1]`. Any attempt to access a bit at a coordinate `column<0 || column>=columns() || row<0 || row>=rows()` will throw an `IndexOutOfBoundsException`. Operations involving two bit matrices (like AND, OR, XOR, etc.) will throw an `IllegalArgumentException` if both bit matrices do not have the same number of columns and rows.

If you need extremely quick access to individual bits: Although getting and setting individual bits with methods `get(...)` and `put(...)` is quick, it is even quicker (but not safe) to use `getQuick(...)` and `putQuick(...)`.

Note that this implementation is not synchronized.

Version:
  1.0, 09/24/99
See Also:
  `BitVector`, `QuickBitVector`, `BitSet`, Serialized Form

Field Summary

Fields inherited from class cern.colt.PersistentObject
`serialVersionUID`

Constructor Summary
`BitMatrix(int columns, int rows)` Constructs a bit matrix with a given number of columns and rows.

Method Summary
`void` | `and(BitMatrix other)` Performs a logical AND of the receiver with another bit matrix.
`void` | `andNot(BitMatrix other)` Clears all of the bits in receiver whose corresponding bit is set in the other bit matrix.
`int` | `cardinality()` Returns the number of bits currently in the `true` state.
`void` | `clear()` Clears all bits of the receiver.
`Object` | `clone()` Cloning this `BitMatrix` produces a new `BitMatrix` that is equal to it.
`int` | `columns()` Returns the number of columns of the receiver.
`BitMatrix` | `copy()` Returns a shallow clone of the receiver; calls `clone()` and casts the result.
`boolean` | `equals(Object obj)` Compares this object against the specified object.
`boolean` | `forEachCoordinateInState(boolean state, IntIntProcedure procedure)` Applies a procedure to each coordinate that holds a bit in the given state.
`boolean` | `get(int column, int row)` Returns from the receiver the value of the bit at the specified coordinate.
`boolean` | `getQuick(int column, int row)` Returns from the receiver the value of the bit at the specified coordinate; WARNING: Does not check preconditions.
`int` | `hashCode()` Returns a hash code value for the receiver.
`void` | `not()` Performs a logical NOT on the bits of the receiver.
`void` | `or(BitMatrix other)` Performs a logical OR of the receiver with another bit matrix.
`BitMatrix` | `part(int column, int row, int width, int height)` Constructs and returns a new matrix with `width` columns and `height` rows which is a copy of the contents of the given box.
`void` | `put(int column, int row, boolean value)` Sets the bit at the specified coordinate to the state specified by `value`.
`void` | `putQuick(int column, int row, boolean value)` Sets the bit at the specified coordinate to the state specified by `value`; WARNING: Does not check preconditions.
`void` | `replaceBoxWith(int column, int row, int width, int height, BitMatrix source, int sourceColumn, int sourceRow)` Replaces a box of the receiver with the contents of another matrix's box.
`void` | `replaceBoxWith(int column, int row, int width, int height, boolean value)` Sets the bits in the given box to the state specified by `value`.
`int` | `rows()` Returns the number of rows of the receiver.
`int` | `size()` Returns the size of the receiver which is `columns()*rows()`.
`BitVector` | `toBitVector()` Converts the receiver to a bitvector.
`String` | `toString()` Returns a (very crude) string representation of the receiver.
`void` | `xor(BitMatrix other)` Performs a logical XOR of the receiver with another bit matrix.

Methods inherited from class java.lang.Object
`getClass, notify, notifyAll, wait, wait, wait`

Constructor Detail

### BitMatrix

    public BitMatrix(int columns,
                     int rows)

  Constructs a bit matrix with a given number of columns and rows. All bits are initially `false`.

Parameters:
  `columns` - the number of columns the matrix shall have.
  `rows` - the number of rows the matrix shall have.
Throws:
  `IllegalArgumentException` - if `columns < 0 || rows < 0`.

Method Detail

### and

    public void and(BitMatrix other)

  Performs a logical AND of the receiver with another bit matrix. The receiver is modified so that a bit in it has the value `true` if and only if it already had the value `true` and the corresponding bit in the other bit matrix argument has the value `true`.

  Parameters:
    `other` - a bit matrix.
  Throws:
    `IllegalArgumentException` - if `columns() != other.columns() || rows() != other.rows()`.

### andNot

    public void andNot(BitMatrix other)

  Clears all of the bits in receiver whose corresponding bit is set in the other bit matrix. In other words, determines the difference (A\B) between two bit matrices.

  Parameters:
    `other` - a bit matrix with which to mask the receiver.
  Throws:
    `IllegalArgumentException` - if `columns() != other.columns() || rows() != other.rows()`.

### cardinality

    public int cardinality()

  Returns the number of bits currently in the `true` state. Optimized for speed. Particularly quick if the receiver is either sparse or dense.

### clear

    public void clear()

  Clears all bits of the receiver.

### clone

    public Object clone()

  Cloning this `BitMatrix` produces a new `BitMatrix` that is equal to it. The clone of the bit matrix is another bit matrix that has exactly the same bits set to `true` as this bit matrix and the same number of columns and rows.

  Overrides:
    `clone` in class `PersistentObject`
  Returns:
    a clone of this bit matrix.

### columns

    public int columns()

  Returns the number of columns of the receiver.

### copy

    public BitMatrix copy()

  Returns a shallow clone of the receiver; calls `clone()` and casts the result.

  Returns:
    a shallow clone of the receiver.

### equals

    public boolean equals(Object obj)

  Compares this object against the specified object. The result is `true` if and only if the argument is not `null` and is a `BitMatrix` object that has the same number of columns and rows as the receiver and that has exactly the same bits set to `true` as the receiver.

  Parameters:
    `obj` - the object to compare with.
  Returns:
    `true` if the objects are the same; `false` otherwise.

### forEachCoordinateInState

    public boolean forEachCoordinateInState(boolean state,
                                            IntIntProcedure procedure)

  Applies a procedure to each coordinate that holds a bit in the given state. Iterates rowwise downwards from [columns()-1,rows()-1] to [0,0]. Useful, for example, if you want to copy bits into an image or somewhere else. Optimized for speed. Particularly quick if one of the following conditions holds
  - `state==true` and the receiver is sparse (`cardinality()` is small compared to `size()`).
  - `state==false` and the receiver is dense (`cardinality()` is large compared to `size()`).

  Parameters:
    `state` - element to search for.
    `procedure` - a procedure object taking as first argument the current column and as second argument the current row. Stops iteration if the procedure returns `false`, otherwise continues.
  Returns:
    `false` if the procedure stopped before all elements where iterated over, `true` otherwise.

### get

    public boolean get(int column,
                       int row)

  Returns from the receiver the value of the bit at the specified coordinate. The value is `true` if this bit is currently set; otherwise, returns `false`.

  Parameters:
    `column` - the index of the column-coordinate.
    `row` - the index of the row-coordinate.
  Returns:
    the value of the bit at the specified coordinate.
  Throws:
    `IndexOutOfBoundsException` - if `column<0 || column>=columns() || row<0 || row>=rows()`

### getQuick

    public boolean getQuick(int column,
                            int row)

  Returns from the receiver the value of the bit at the specified coordinate; WARNING: Does not check preconditions. The value is `true` if this bit is currently set; otherwise, returns `false`.

  Provided with invalid parameters this method may return invalid values without throwing any exception. You should only use this method when you are absolutely sure that the coordinate is within bounds. Precondition (unchecked): `column>=0 && column<columns() && row>=0 && row<rows()`.

  Parameters:
    `column` - the index of the column-coordinate.
    `row` - the index of the row-coordinate.
  Returns:
    the value of the bit at the specified coordinate.

### hashCode

    public int hashCode()

  Returns a hash code value for the receiver.

### not

    public void not()

  Performs a logical NOT on the bits of the receiver.

### or

    public void or(BitMatrix other)

  Performs a logical OR of the receiver with another bit matrix. The receiver is modified so that a bit in it has the value `true` if and only if it either already had the value `true` or the corresponding bit in the other bit matrix argument has the value `true`.

  Parameters:
    `other` - a bit matrix.
  Throws:
    `IllegalArgumentException` - if `columns() != other.columns() || rows() != other.rows()`.

### part

    public BitMatrix part(int column,
                          int row,
                          int width,
                          int height)

  Constructs and returns a new matrix with `width` columns and `height` rows which is a copy of the contents of the given box. The box ranges from `[column,row]` to `[column+width-1,row+height-1]`, all inclusive.

  Parameters:
    `column` - the index of the column-coordinate.
    `row` - the index of the row-coordinate.
    `width` - the width of the box.
    `height` - the height of the box.
  Throws:
    `IndexOutOfBoundsException` - if `column<0 || column+width>columns() || row<0 || row+height>rows()`

### put

    public void put(int column,
                    int row,
                    boolean value)

  Sets the bit at the specified coordinate to the state specified by `value`.

  Parameters:
    `column` - the index of the column-coordinate.
    `row` - the index of the row-coordinate.
    `value` - the value of the bit to be copied into the specified coordinate.
  Throws:
    `IndexOutOfBoundsException` - if `column<0 || column>=columns() || row<0 || row>=rows()`

### putQuick

    public void putQuick(int column,
                         int row,
                         boolean value)

  Sets the bit at the specified coordinate to the state specified by `value`; WARNING: Does not check preconditions.

  Provided with invalid parameters this method may return invalid values without throwing any exception. You should only use this method when you are absolutely sure that the coordinate is within bounds. Precondition (unchecked): `column>=0 && column<columns() && row>=0 && row<rows()`.

  Parameters:
    `column` - the index of the column-coordinate.
    `row` - the index of the row-coordinate.
    `value` - the value of the bit to be copied into the specified coordinate.

### replaceBoxWith

    public void replaceBoxWith(int column,
                               int row,
                               int width,
                               int height,
                               BitMatrix source,
                               int sourceColumn,
                               int sourceRow)

  Replaces a box of the receiver with the contents of another matrix's box. The source box ranges from `[sourceColumn,sourceRow]` to `[sourceColumn+width-1,sourceRow+height-1]`, all inclusive. The destination box ranges from `[column,row]` to `[column+width-1,row+height-1]`, all inclusive. Does nothing if `width <= 0 || height <= 0`. If `source==this` and the source and destination box intersect in an ambiguous way, then replaces as if using an intermediate auxiliary copy of the receiver.

  Parameters:
    `column` - the index of the column-coordinate.
    `row` - the index of the row-coordinate.
    `width` - the width of the box.
    `height` - the height of the box.
    `source` - the source matrix to copy from(may be identical to the receiver).
    `sourceColumn` - the index of the source column-coordinate.
    `sourceRow` - the index of the source row-coordinate.
  Throws:
    `IndexOutOfBoundsException` - if `column<0 || column+width>columns() || row<0 || row+height>rows()`
    `IndexOutOfBoundsException` - if `sourceColumn<0 || sourceColumn+width>source.columns() || sourceRow<0 || sourceRow+height>source.rows()`

### replaceBoxWith

    public void replaceBoxWith(int column,
                               int row,
                               int width,
                               int height,
                               boolean value)

  Sets the bits in the given box to the state specified by `value`. The box ranges from `[column,row]` to `[column+width-1,row+height-1]`, all inclusive. (Does nothing if `width <= 0 || height <= 0`).

  Parameters:
    `column` - the index of the column-coordinate.
    `row` - the index of the row-coordinate.
    `width` - the width of the box.
    `height` - the height of the box.
    `value` - the value of the bit to be copied into the bits of the specified box.
  Throws:
    `IndexOutOfBoundsException` - if `column<0 || column+width>columns() || row<0 || row+height>rows()`

### rows

    public int rows()

  Returns the number of rows of the receiver.

### size

    public int size()

  Returns the size of the receiver which is `columns()*rows()`.

### toBitVector

    public BitVector toBitVector()

  Converts the receiver to a bitvector. In many cases this method only makes sense on one-dimensional matrices. WARNING: The returned bitvector and the receiver share the same backing bits. Modifying either of them will affect the other. If this behaviour is not what you want, you should first use `copy()` to make sure both objects use separate internal storage.

### toString

    public String toString()

  Returns a (very crude) string representation of the receiver.

### xor

    public void xor(BitMatrix other)

  Performs a logical XOR of the receiver with another bit matrix. The receiver is modified so that a bit in it has the value `true` if and only if one of the following statements holds:
  - The bit initially has the value `true`, and the corresponding bit in the argument has the value `false`.
  - The bit initially has the value `false`, and the corresponding bit in the argument has the value `true`.

  Parameters:
    `other` - a bit matrix.
  Throws:
    `IllegalArgumentException` - if `columns() != other.columns() || rows() != other.rows()`.

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