KeyAnalyzer (Apache Commons Collections 4.0 API)

java.lang.Object
- org.apache.commons.collections4.trie.KeyAnalyzer<K>

All Implemented Interfaces:

Serializable, Comparator<K>

Direct Known Subclasses:

StringKeyAnalyzer
```
public abstract class KeyAnalyzer<K>
extends Object
implements Comparator<K>, Serializable
```
Defines the interface to analyze Trie keys on a bit level. KeyAnalyzer's methods return the length of the key in bits, whether or not a bit is set, and bits per element in the key.
Additionally, a method determines if a key is a prefix of another key and returns the bit index where one key is different from another key (if the key and found key are equal than the return value is EQUAL_BIT_KEY).

Since:

4.0

Version:

$Id: KeyAnalyzer.java 1491621 2013-06-10 22:05:38Z tn $

See Also:
Serialized Form

Field Summary

Fields
Modifier and Type	Field and Description
`static int`	`EQUAL_BIT_KEY` Returned by `bitIndex(Object, int, int, Object, int, int)` if key and found key are equal.
`static int`	`NULL_BIT_KEY` Returned by `bitIndex(Object, int, int, Object, int, int)` if key's bits are all 0.
`static int`	`OUT_OF_BOUNDS_BIT_KEY`

Constructor Summary

Constructors
Constructor and Description

KeyAnalyzer()

Constructors
Constructor and Description
`KeyAnalyzer()`

Method Summary

Methods
Modifier and Type	Method and Description
`abstract int`	`bitIndex(K key, int offsetInBits, int lengthInBits, K other, int otherOffsetInBits, int otherLengthInBits)` Returns the n-th different bit between key and other.
`abstract int`	`bitsPerElement()` Returns the number of bits per element in the key.
`int`	`compare(K o1, K o2)`
`abstract boolean`	`isBitSet(K key, int bitIndex, int lengthInBits)` Returns whether or not a bit is set.
`abstract boolean`	`isPrefix(K prefix, int offsetInBits, int lengthInBits, K key)` Determines whether or not the given prefix (from offset to length) is a prefix of the given key.
`abstract int`	`lengthInBits(K key)` Returns the length of the Key in bits.

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

Methods inherited from interface java.util.Comparator
equals

- Field Detail
  - NULL_BIT_KEY
```
public static final int NULL_BIT_KEY
```
    Returned by bitIndex(Object, int, int, Object, int, int) if key's bits are all 0.
    
    See Also:
    Constant Field Values
  - EQUAL_BIT_KEY
```
public static final int EQUAL_BIT_KEY
```
    Returned by bitIndex(Object, int, int, Object, int, int) if key and found key are equal. This is a very very specific case and shouldn't happen on a regular basis.
    
    See Also:
    Constant Field Values
  - OUT_OF_BOUNDS_BIT_KEY
```
public static final int OUT_OF_BOUNDS_BIT_KEY
```
    See Also:
    Constant Field Values
- Constructor Detail
  - KeyAnalyzer
```
public KeyAnalyzer()
```
- Method Detail
  - bitsPerElement
```
public abstract int bitsPerElement()
```
    Returns the number of bits per element in the key. This is only useful for variable-length keys, such as Strings.
    
    Returns:
    the number of bits per element
  - lengthInBits
```
public abstract int lengthInBits(K key)
```
    Returns the length of the Key in bits.
    
    Parameters:
    key - the key
    
    Returns:
    the bit length of the key
  - isBitSet
```
public abstract boolean isBitSet(K key,
               int bitIndex,
               int lengthInBits)
```
    Returns whether or not a bit is set.
    
    Parameters:
    key - the key to check, may not be null
    bitIndex - the bit index to check
    lengthInBits - the maximum key length in bits to check
    
    Returns:
    true if the bit is set in the given key and bitIndex < lengthInBits, false otherwise.
  - bitIndex
```
public abstract int bitIndex(K key,
           int offsetInBits,
           int lengthInBits,
           K other,
           int otherOffsetInBits,
           int otherLengthInBits)
```
    Returns the n-th different bit between key and other. This starts the comparison in key at 'offsetInBits' and goes for 'lengthInBits' bits, and compares to the other key starting at 'otherOffsetInBits' and going for 'otherLengthInBits' bits.
    
    Parameters:
    key - the key to use
    offsetInBits - the bit offset in the key
    lengthInBits - the maximum key length in bits to use
    other - the other key to use
    otherOffsetInBits - the bit offset in the other key
    otherLengthInBits - the maximum key length in bits for the other key
    
    Returns:
    the bit index where the key and other first differ
  - isPrefix
```
public abstract boolean isPrefix(K prefix,
               int offsetInBits,
               int lengthInBits,
               K key)
```
    Determines whether or not the given prefix (from offset to length) is a prefix of the given key.
    
    Parameters:
    prefix - the prefix to check
    offsetInBits - the bit offset in the key
    lengthInBits - the maximum key length in bits to use
    key - the key to check
    
    Returns:
    true if this is a valid prefix for the given key
  - compare
```
public int compare(K o1,
          K o2)
```
    Specified by:
    
    compare in interface Comparator<K>

Class KeyAnalyzer<K>

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Methods inherited from interface java.util.Comparator

Field Detail

NULL_BIT_KEY

EQUAL_BIT_KEY

OUT_OF_BOUNDS_BIT_KEY

Constructor Detail

KeyAnalyzer

Method Detail

bitsPerElement

lengthInBits

isBitSet

bitIndex

isPrefix

compare