```
public final class SparseArray
extends Object
```
Sparse array encoding utilities. Sparse means an index and its value are kept in an array as a pair.

All Methods Static Methods Concrete Methods
Modifier and Type	Method	Description
`static int`	`countUnique(int[] buffer, int fromIndex, int toIndex)`	Count unique values in the sorted array.
`static int[]`	`mergeSparseArrays(Iterable<int[]> source)`	Merge data from one or more sparse arrays.
`static String`	`sparseToString(int[] intIntArray)`	Convert an int-int compact mapping array to a string.
`static int[]`	`toSparseEncoding(com.carrotsearch.hppc.IntStack documents)`	Convert a list of documents to sparse document-count representation.
`static int[]`	`toSparseEncodingByHash(com.carrotsearch.hppc.IntStack documents)`	Convert to sparse encoding using a hash map.
`static int[]`	`toSparseEncodingBySort(com.carrotsearch.hppc.IntStack documents)`	Convert to sparse encoding using sorting and counting.

public static int[] toSparseEncoding(com.carrotsearch.hppc.IntStack documents)

Convert a list of documents to sparse document-count representation.

public static int[] toSparseEncodingByHash(com.carrotsearch.hppc.IntStack documents)

Convert to sparse encoding using a hash map.

public static int[] toSparseEncodingBySort(com.carrotsearch.hppc.IntStack documents)

Convert to sparse encoding using sorting and counting.

public static int countUnique(int[] buffer,
                              int fromIndex,
                              int toIndex)

Count unique values in the sorted array.

public static int[] mergeSparseArrays(Iterable<int[]> source)

Merge data from one or more sparse arrays.

sparseToString
```
public static String sparseToString(int[] intIntArray)
```
Convert an int-int compact mapping array to a string.

Class SparseArray