FrequencyTrackingRingBuffer

java.lang.Object
- org.apache.lucene.util.FrequencyTrackingRingBuffer

All Implemented Interfaces:

Accountable
```
public final class FrequencyTrackingRingBuffer
extends java.lang.Object
implements Accountable
```
A ring buffer that tracks the frequency of the integers that it contains. This is typically useful to track the hash codes of popular recently-used items. This data-structure requires 22 bytes per entry on average (between 16 and 28).

Nested Class Summary

Nested Classes
Modifier and Type Class Description

private static class FrequencyTrackingRingBuffer.IntBag
A bag of integers.

Field Summary

Fields
Modifier and Type	Field	Description
`private static long`	`BASE_RAM_BYTES_USED`
`private int[]`	`buffer`
`private FrequencyTrackingRingBuffer.IntBag`	`frequencies`
`private int`	`maxSize`
`private int`	`position`

Fields inherited from interface org.apache.lucene.util.Accountable
NULL_ACCOUNTABLE

Constructor Summary

Constructors
Constructor Description

FrequencyTrackingRingBuffer(int maxSize, int sentinel)
Create a new ring buffer that will contain at most maxSize items.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`add(int i)`	Add a new item to this ring buffer, potentially removing the oldest entry from this buffer if it is already full.
`(package private) java.util.Map<java.lang.Integer,java.lang.Integer>`	`asFrequencyMap()`
`int`	`frequency(int key)`	Returns the frequency of the provided key in the ring buffer.
`long`	`ramBytesUsed()`	Return the memory usage of this object in bytes.

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

Methods inherited from interface org.apache.lucene.util.Accountable
getChildResources

- Field Detail
  - BASE_RAM_BYTES_USED
```
private static final long BASE_RAM_BYTES_USED
```
  - maxSize
```
private final int maxSize
```
  - buffer
```
private final int[] buffer
```
  - position
```
private int position
```
  - frequencies
```
private final FrequencyTrackingRingBuffer.IntBag frequencies
```
- Constructor Detail
  - FrequencyTrackingRingBuffer
```
public FrequencyTrackingRingBuffer(int maxSize,
                                   int sentinel)
```
    Create a new ring buffer that will contain at most maxSize items. This buffer will initially contain maxSize times the sentinel value.
- Method Detail
  - ramBytesUsed
```
public long ramBytesUsed()
```
    Description copied from interface: Accountable
    
    Return the memory usage of this object in bytes. Negative values are illegal.
    
    Specified by:
    
    ramBytesUsed in interface Accountable
  - add
```
public void add(int i)
```
    Add a new item to this ring buffer, potentially removing the oldest entry from this buffer if it is already full.
  - frequency
```
public int frequency(int key)
```
    Returns the frequency of the provided key in the ring buffer.
  - asFrequencyMap
```
java.util.Map<java.lang.Integer,java.lang.Integer> asFrequencyMap()
```