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 and Description
    --- | ---
    `protected` | `RadixSelector(int maxLength)` Sole constructor.

  - ### Method Summary

    All Methods Instance Methods Abstract Methods Concrete Methods
    Modifier and Type | Method and 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 Detail

    - #### RadixSelector

          protected RadixSelector(int maxLength)

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

  - ### Method Detail

    - #### 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 `i` 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`

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