Top Description Fields Constructors Methods
org.apache.derby.iapi.util

public final Class JBitSet

extends Object
Class Inheritance
Imports
org.apache.derby.shared.common.sanity.SanityManager, java.util.BitSet
JBitSet is a wrapper class for BitSet. It is a fixed length implementation which can be extended via the grow() method. It provides additional methods to manipulate BitSets.

Note

JBitSet was driven by the (current and perceived) needs of the optimizer, but placed in the util package since it is not specific to query trees..

Note

java.util.BitSet is final, so we must provide a wrapper class which includes a BitSet member in order to extend the functionality. We want to make it look like JBitSet extends BitSet, so we need to provide wrapper methods for all of BitSet's methods.

Field Summary

Modifier and TypeField and Description
private final BitSet
bitSet

private int
size

Constructor Summary

AccessConstructor and Description
public
JBitSet(int
The number of bits in the JBitSet.
size)

Construct a JBitSet of the specified size.

private
JBitSet(BitSet
The BitSet.
bitSet, int
The size of bitSet.

Note

We need to specify the size since the size of a BitSet is not guaranteed to be the same as JBitSet.size().

size)

Construct a JBitSet with the specified bitSet.

Method Summary

Modifier and TypeMethod and Description
public void
and(JBitSet set)

public void
clear(int bitIndex)

public void
clearAll()

Clear all of the bits in this JBitSet

public Object
clone()

Overrides java.lang.Object.clone.

Creates and returns a copy of this object.

public boolean

Returns:

boolean Whether or not jBitSet is a subset.
contains(JBitSet
JBitSet that we want to know if it is a subset of current JBitSet
jBitSet)

Test to see if one JBitSet contains another one of the same size.

public boolean
equals(Object
the reference object with which to compare.
obj)

Overrides java.lang.Object.equals.

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

public boolean
get(int bitIndex)

public int

Returns:

int Index of first set bit, -1 if none set.
getFirstSetBit()

Get the first set bit (starting at index 0) from a JBitSet.

public void
grow(int
The new size
newSize)

Grow an existing JBitSet to the specified size.

public int
hashCode()

Overrides java.lang.Object.hashCode.

Returns a hash code value for this object.

public boolean

Returns:

boolean Whether or not JBitSet has a single bit set.
hasSingleBitSet()

See of a JBitSet has exactly 1 bit set.

public void
or(JBitSet set)

public void
set(int bitIndex)

public void
setTo(JBitSet
The JBitSet to copy.
sourceBitSet)

Set the BitSet to have the exact same bits set as the parameter's BitSet.

public int

Returns:

int Size of bitSet
size()

Return the size of bitSet

public String
toString()

Overrides java.lang.Object.toString.

Returns a string representation of the object.

public void
xor(JBitSet set)

Inherited from java.lang.Object:
finalizegetClassnotifynotifyAllwaitwaitwait

Field Detail

bitSetback to summary
private final BitSet bitSet
sizeback to summary
private int size

Constructor Detail

JBitSetback to summary
public JBitSet(int size)

Construct a JBitSet of the specified size.

Parameters
size:int

The number of bits in the JBitSet.

JBitSetback to summary
private JBitSet(BitSet bitSet, int size)

Construct a JBitSet with the specified bitSet.

Parameters
bitSet:BitSet

The BitSet.

size:int

The size of bitSet.

Note

We need to specify the size since the size of a BitSet is not guaranteed to be the same as JBitSet.size().

Method Detail

andback to summary
public void and(JBitSet set)
clearback to summary
public void clear(int bitIndex)
clearAllback to summary
public void clearAll()

Clear all of the bits in this JBitSet

cloneback to summary
public Object clone()

Overrides java.lang.Object.clone.

Doc from java.lang.Object.clone.

Creates and returns a copy of this object. The precise meaning of "copy" may depend on the class of the object. The general intent is that, for any object x, the expression: 

x.clone() != x
will be true, and that the expression: 
x.clone().getClass() == x.getClass()
will be true, but these are not absolute requirements. While it is typically the case that: 
x.clone().equals(x)
will be true, this is not an absolute requirement.

By convention, the returned object should be obtained by calling super.clone. If a class and all of its superclasses (except Object) obey this convention, it will be the case that x.clone().getClass() == x.getClass().

By convention, the object returned by this method should be independent of this object (which is being cloned). To achieve this independence, it may be necessary to modify one or more fields of the object returned by super.clone before returning it. Typically, this means copying any mutable objects that comprise the internal "deep structure" of the object being cloned and replacing the references to these objects with references to the copies. If a class contains only primitive fields or references to immutable objects, then it is usually the case that no fields in the object returned by super.clone need to be modified.

Returns:Object

a clone of this instance.

containsback to summary
public boolean contains(JBitSet jBitSet)

Test to see if one JBitSet contains another one of the same size.

Parameters
jBitSet:JBitSet

JBitSet that we want to know if it is a subset of current JBitSet

Returns:boolean

boolean Whether or not jBitSet is a subset.

equalsback to summary
public boolean equals(Object obj)

Overrides java.lang.Object.equals.

Doc from java.lang.Object.equals.

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.

An equivalence relation partitions the elements it operates on into equivalence classes; all the members of an equivalence class are equal to each other. Members of an equivalence class are substitutable for each other, at least for some purposes.

Parameters
obj:Object

the reference object with which to compare.

Returns:boolean

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

getback to summary
public boolean get(int bitIndex)
getFirstSetBitback to summary
public int getFirstSetBit()

Get the first set bit (starting at index 0) from a JBitSet.

Returns:int

int Index of first set bit, -1 if none set.

growback to summary
public void grow(int newSize)

Grow an existing JBitSet to the specified size.

Parameters
newSize:int

The new size

hashCodeback to summary
public int hashCode()

Overrides java.lang.Object.hashCode.

Doc from java.lang.Object.hashCode.

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

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 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 equals 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 hash tables.
Returns:int

a hash code value for this object

hasSingleBitSetback to summary
public boolean hasSingleBitSet()

See of a JBitSet has exactly 1 bit set.

Returns:boolean

boolean Whether or not JBitSet has a single bit set.

orback to summary
public void or(JBitSet set)
setback to summary
public void set(int bitIndex)
setToback to summary
public void setTo(JBitSet sourceBitSet)

Set the BitSet to have the exact same bits set as the parameter's BitSet.

Parameters
sourceBitSet:JBitSet

The JBitSet to copy.

sizeback to summary
public int size()

Return the size of bitSet

Returns:int

int Size of bitSet

toStringback to summary
public String toString()

Overrides java.lang.Object.toString.

Doc from java.lang.Object.toString.

Returns a string representation of the object. Satisfying this method's contract implies a non-null result must be returned.

Returns:String

a string representation of the object

xorback to summary
public void xor(JBitSet set)