Package org.apache.lucene.util

# Class RadixSelector

java.lang.Object
org.apache.lucene.util.Selector
org.apache.lucene.util.RadixSelector

public abstract class RadixSelector extends Selector
Radix selector.

This implementation works similarly to a MSB radix sort except that it only recurses into the sub partition that contains the desired value.

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

## Constructor Summary

Constructors
Modifier
Constructor
Description
`protected`
`RadixSelector(int maxLength)`
Sole constructor.

## Method Summary

Modifier and Type
Method
Description
`protected abstract int`
`byteAt(int i, int k)`
Return the k-th byte of the entry at index `i`, or `-1` if its length is less than or equal to `k`.
`protected Selector`
`getFallbackSelector(int d)`
Get a fall-back selector which may assume that the first `d` bytes of all compared strings are equal.
`void`
`select(int from, int to, int k)`
Reorder elements so that the element at position `k` is the same as if all elements were sorted and all other elements are partitioned around it: `[from, k)` only contains elements that are less than or equal to `k` and `(k, to)` only contains elements that are greater than or equal to `k`.

### Methods inherited from class org.apache.lucene.util.Selector

`swap`

### Methods inherited from class java.lang.Object

`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

## Constructor Details

### RadixSelector

protected RadixSelector(int maxLength)
Sole constructor.

Parameters:
  `maxLength` - the maximum length of keys, pass `Integer.MAX_VALUE` if unknown.

## Method Details

### byteAt

protected abstract int byteAt(int i, int k)
Return the k-th byte of the entry at index `i`, or `-1` if its length is less than or equal to `k`. This may only be called with a value of `k` between `0` included and `maxLength` excluded.

### getFallbackSelector

protected Selector getFallbackSelector(int d)
Get a fall-back selector which may assume that the first `d` bytes of all compared strings are equal. This fallback selector is used when the range becomes narrow or when the maximum level of recursion has been exceeded.

### select

public void select(int from, int to, int k)
Description copied from class: `Selector`
Reorder elements so that the element at position `k` is the same as if all elements were sorted and all other elements are partitioned around it: `[from, k)` only contains elements that are less than or equal to `k` and `(k, to)` only contains elements that are greater than or equal to `k`.

Specified by:
  `select` in class `Selector`