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## org.apache.lucene.util
Class BitVector

    java.lang.Object
      org.apache.lucene.util.BitVector

All Implemented Interfaces:
  Cloneable, Bits

    public final class BitVector

extends Object
implements Cloneable, Bits

Optimized implementation of a vector of bits. This is more-or-less like java.util.BitSet, but also includes the following:

- a count() method, which efficiently computes the number of one bits;
- optimized read from and write to disk;
- inlinable get() method;
- store and load, as bit set or d-gaps, depending on sparseness;

NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.lucene.util.Bits
`Bits.MatchAllBits, Bits.MatchNoBits`

Field Summary

Fields inherited from interface org.apache.lucene.util.Bits
`EMPTY_ARRAY`

Constructor Summary
`BitVector(Directory d, String name)` Constructs a bit vector from the file `name` in Directory `d`, as written by the `write(org.apache.lucene.store.Directory, java.lang.String)` method.
`BitVector(int n)` Constructs a vector capable of holding `n` bits.

Method Summary
`void` | `clear(int bit)` Sets the value of `bit` to zero.
`Object` | `clone()`
`int` | `count()` Returns the total number of one bits in this vector.
`boolean` | `get(int bit)` Returns `true` if `bit` is one and `false` if it is zero.
`boolean` | `getAndSet(int bit)` Sets the value of `bit` to true, and returns true if bit was already set
`int` | `getRecomputedCount()` For testing
`int` | `length()` Returns the number of bits in this vector.
`void` | `set(int bit)` Sets the value of `bit` to one.
`int` | `size()` Returns the number of bits in this vector.
`void` | `write(Directory d, String name)` Writes this vector to the file `name` in Directory `d`, in a format that can be read by the constructor `BitVector(Directory, String)`.

Methods inherited from class java.lang.Object
`equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### BitVector

    public BitVector(int n)

  Constructs a vector capable of holding `n` bits.

### BitVector

    public BitVector(Directory d,
                     String name)
              throws IOException

  Constructs a bit vector from the file `name` in Directory `d`, as written by the `write(org.apache.lucene.store.Directory, java.lang.String)` method.

  Throws:
    `IOException`

Method Detail

### clone

    public Object clone()

  Overrides:
    `clone` in class `Object`

### set

    public final void set(int bit)

  Sets the value of `bit` to one.

### getAndSet

    public final boolean getAndSet(int bit)

  Sets the value of `bit` to true, and returns true if bit was already set

### clear

    public final void clear(int bit)

  Sets the value of `bit` to zero.

### get

    public final boolean get(int bit)

  Returns `true` if `bit` is one and `false` if it is zero.

  Specified by:
    `get` in interface `Bits`

### size

    public final int size()

  Returns the number of bits in this vector. This is also one greater than the number of the largest valid bit number.

### length

    public final int length()

  Returns the number of bits in this vector. This is also one greater than the number of the largest valid bit number.

  Specified by:
    `length` in interface `Bits`

### count

    public final int count()

  Returns the total number of one bits in this vector. This is efficiently computed and cached, so that, if the vector is not changed, no recomputation is done for repeated calls.

### getRecomputedCount

    public final int getRecomputedCount()

  For testing

### write

    public final void write(Directory d,
                            String name)
                     throws IOException

  Writes this vector to the file `name` in Directory `d`, in a format that can be read by the constructor `BitVector(Directory, String)`.

  Throws:
    `IOException`

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