AlphabeticIndex (ICU4J 76)

java.lang.Object
- com.ibm.icu.text.AlphabeticIndex<V>

All Implemented Interfaces:

Iterable<AlphabeticIndex.Bucket<V>>
```
public final class AlphabeticIndex<V>
extends Object
implements Iterable<AlphabeticIndex.Bucket<V>>
```
AlphabeticIndex supports the creation of a UI index appropriate for a given language. It can support either direct use, or use with a client that doesn't support localized collation. The following is an example of what an index might look like in a UI:
```
  ... A B C D E F G H I J K L M N O P Q R S T U V W X Y Z  ...

  A
     Addison
     Albertson
     Azensky
  B
     Baecker
  ...
 
```
The class can generate a list of labels for use as a UI "index", that is, a list of clickable characters (or character sequences) that allow the user to see a segment (bucket) of a larger "target" list. That is, each label corresponds to a bucket in the target list, where everything in the bucket is greater than or equal to the character (according to the locale's collation). Strings can be added to the index; they will be in sorted order in the right bucket.
The class also supports having buckets for strings before the first (underflow), after the last (overflow), and between scripts (inflow). For example, if the index is constructed with labels for Russian and English, Greek characters would fall into an inflow bucket between the other two scripts.
Note: If you expect to have a lot of ASCII or Latin characters as well as characters from the user's language, then it is a good idea to call addLabels(ULocale.English).
Direct Use

The following shows an example of building an index directly. The "show..." methods below are just to illustrate usage.
```
 // Create a simple index where the values for the strings are Integers, and add the strings

 AlphabeticIndex<Integer> index = new AlphabeticIndex<Integer>(desiredLocale).addLabels(additionalLocale);
 int counter = 0;
 for (String item : test) {
     index.addRecord(item, counter++);
 }
 ...
 // Show index at top. We could skip or gray out empty buckets

 for (AlphabeticIndex.Bucket<Integer> bucket : index) {
     if (showAll || bucket.size() != 0) {
         showLabelAtTop(UI, bucket.getLabel());
     }
 }
  ...
 // Show the buckets with their contents, skipping empty buckets

 for (AlphabeticIndex.Bucket<Integer> bucket : index) {
     if (bucket.size() != 0) {
         showLabelInList(UI, bucket.getLabel());
         for (AlphabeticIndex.Record<Integer> item : bucket) {
             showIndexedItem(UI, item.getName(), item.getData());
         }
 
```
The caller can build different UIs using this class. For example, an index character could be omitted or grayed-out if its bucket is empty. Small buckets could also be combined based on size, such as:
```
 ... A-F G-N O-Z ...
 
```
Client Support

Callers can also use the AlphabeticIndex.ImmutableIndex, or the AlphabeticIndex itself, to support sorting on a client that doesn't support AlphabeticIndex functionality.
The ImmutableIndex is both immutable and thread-safe. The corresponding AlphabeticIndex methods are not thread-safe because they "lazily" build the index buckets.
- ImmutableIndex.getBucket(index) provides random access to all buckets and their labels and label types.
- AlphabeticIndex.getBucketLabels() or the bucket iterator on either class can be used to get a list of the labels, such as "...", "A", "B",..., and send that list to the client.
- When the client has a new name, it sends that name to the server. The server needs to call the following methods, and communicate the bucketIndex and collationKey back to the client.
```
 int bucketIndex = index.getBucketIndex(name);
 String label = immutableIndex.getBucket(bucketIndex).getLabel();  // optional
 RawCollationKey collationKey = collator.getRawCollationKey(name, null);
 
```
- The client would put the name (and associated information) into its bucket for bucketIndex. The collationKey is a sequence of bytes that can be compared with a binary compare, and produce the right localized result.
Author:

Mark Davis

Status:
Stable ICU 4.8.

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`static class`	`AlphabeticIndex.Bucket<V>` An index "bucket" with a label string and type.
`static class`	`AlphabeticIndex.ImmutableIndex<V>` Immutable, thread-safe version of `AlphabeticIndex`.
`static class`	`AlphabeticIndex.Record<V>` A (name, data) pair, to be sorted by name into one of the index buckets.

Constructor Summary

Constructors
Constructor and Description
`AlphabeticIndex(Locale locale)` Create the index object.
`AlphabeticIndex(RuleBasedCollator collator)` Create an AlphabeticIndex that uses a specific collator.
`AlphabeticIndex(ULocale locale)` Create the index object.

Method Summary

All Methods Instance Methods Concrete Methods Deprecated Methods
Modifier and Type	Method and Description
`AlphabeticIndex<V>`	`addLabels(Locale... additions)` Add more index characters (aside from what are in the locale)
`AlphabeticIndex<V>`	`addLabels(ULocale... additions)` Add more index characters (aside from what are in the locale)
`AlphabeticIndex<V>`	`addLabels(UnicodeSet additions)` Add more index characters (aside from what are in the locale)
`AlphabeticIndex<V>`	`addRecord(CharSequence name, V data)` Add a record (name and data) to the index.
`AlphabeticIndex.ImmutableIndex<V>`	`buildImmutableIndex()` Builds an immutable, thread-safe version of this instance, without data records.
`AlphabeticIndex<V>`	`clearRecords()` Clear the index.
`int`	`getBucketCount()` Return the number of buckets in the index.
`int`	`getBucketIndex(CharSequence name)` Get the bucket number for the given name.
`List<String>`	`getBucketLabels()` Get the labels.
`RuleBasedCollator`	`getCollator()` Get a clone of the collator used internally.
`List<String>`	`getFirstCharactersInScripts()` Deprecated. This API is ICU internal, only for testing.
`String`	`getInflowLabel()` Get the default label used for abbreviated buckets between other labels.
`int`	`getMaxLabelCount()` Get the limit on the number of labels in the index.
`String`	`getOverflowLabel()` Get the default label used in the IndexCharacters' locale for overflow, eg the first item in: ...
`int`	`getRecordCount()` Return the number of records in the index: that is, the total number of distinct <name,data> pairs added with addRecord(...), over all the buckets.
`String`	`getUnderflowLabel()` Get the default label used in the IndexCharacters' locale for underflow, eg the last item in: X Y Z ...
`Iterator<AlphabeticIndex.Bucket<V>>`	`iterator()` Return an iterator over the buckets.
`AlphabeticIndex<V>`	`setInflowLabel(String inflowLabel)` Set the inflowLabel label
`AlphabeticIndex<V>`	`setMaxLabelCount(int maxLabelCount)` Set a limit on the number of labels in the index.
`AlphabeticIndex<V>`	`setOverflowLabel(String overflowLabel)` Set the overflow label
`AlphabeticIndex<V>`	`setUnderflowLabel(String underflowLabel)` Set the underflowLabel label

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

Methods inherited from interface java.lang.Iterable
forEach, spliterator

- Constructor Detail
  - AlphabeticIndex
```
public AlphabeticIndex(ULocale locale)
```
    Create the index object.
    
    Parameters:
    
    locale - The locale for the index.
    
    Status:
    Stable ICU 4.8.
  - AlphabeticIndex
```
public AlphabeticIndex(Locale locale)
```
    Create the index object.
    
    Parameters:
    
    locale - The locale for the index.
    
    Status:
    Stable ICU 4.8.
  - AlphabeticIndex
```
public AlphabeticIndex(RuleBasedCollator collator)
```
    Create an AlphabeticIndex that uses a specific collator.
    The index will be created with no labels; the addLabels() function must be called after creation to add the desired labels to the index.
    The index will work directly with the supplied collator. If the caller will need to continue working with the collator it should be cloned first, so that the collator provided to the AlphabeticIndex remains unchanged after creation of the index.
    
    Parameters:
    
    collator - The collator to use to order the contents of this index.
    
    Status:
    Stable ICU 51.
- Method Detail
  - addLabels
```
public AlphabeticIndex<V> addLabels(UnicodeSet additions)
```
    Add more index characters (aside from what are in the locale)
    
    Parameters:
    
    additions - additional characters to add to the index, such as A-Z.
    
    Returns:
    
    this, for chaining
    
    Status:
    Stable ICU 4.8.
  - addLabels
```
public AlphabeticIndex<V> addLabels(ULocale... additions)
```
    Add more index characters (aside from what are in the locale)
    
    Parameters:
    
    additions - additional characters to add to the index, such as those in Swedish.
    
    Returns:
    
    this, for chaining
    
    Status:
    Stable ICU 4.8.
  - addLabels
```
public AlphabeticIndex<V> addLabels(Locale... additions)
```
    Add more index characters (aside from what are in the locale)
    
    Parameters:
    
    additions - additional characters to add to the index, such as those in Swedish.
    
    Returns:
    
    this, for chaining
    
    Status:
    Stable ICU 4.8.
  - setOverflowLabel
```
public AlphabeticIndex<V> setOverflowLabel(String overflowLabel)
```
    Set the overflow label
    
    Parameters:
    
    overflowLabel - see class description
    
    Returns:
    
    this, for chaining
    
    Status:
    Stable ICU 4.8.
  - getUnderflowLabel
```
public String getUnderflowLabel()
```
    Get the default label used in the IndexCharacters' locale for underflow, eg the last item in: X Y Z ...
    
    Returns:
    
    underflow label
    
    Status:
    Stable ICU 4.8.
  - setUnderflowLabel
```
public AlphabeticIndex<V> setUnderflowLabel(String underflowLabel)
```
    Set the underflowLabel label
    
    Parameters:
    
    underflowLabel - see class description
    
    Returns:
    
    this, for chaining
    
    Status:
    Stable ICU 4.8.
  - getOverflowLabel
```
public String getOverflowLabel()
```
    Get the default label used in the IndexCharacters' locale for overflow, eg the first item in: ... A B C
    
    Returns:
    
    overflow label
    
    Status:
    Stable ICU 4.8.
  - setInflowLabel
```
public AlphabeticIndex<V> setInflowLabel(String inflowLabel)
```
    Set the inflowLabel label
    
    Parameters:
    
    inflowLabel - see class description
    
    Returns:
    
    this, for chaining
    
    Status:
    Stable ICU 4.8.
  - getInflowLabel
```
public String getInflowLabel()
```
    Get the default label used for abbreviated buckets between other labels. For example, consider the labels for Latin and Greek are used: X Y Z ... Α Β Γ.
    
    Returns:
    
    inflow label
    
    Status:
    Stable ICU 4.8.
  - getMaxLabelCount
```
public int getMaxLabelCount()
```
    Get the limit on the number of labels in the index. The number of buckets can be slightly larger: see getBucketCount().
    
    Returns:
    
    maxLabelCount maximum number of labels.
    
    Status:
    Stable ICU 4.8.
  - setMaxLabelCount
```
public AlphabeticIndex<V> setMaxLabelCount(int maxLabelCount)
```
    Set a limit on the number of labels in the index. The number of buckets can be slightly larger: see getBucketCount().
    
    Parameters:
    
    maxLabelCount - Set the maximum number of labels. Currently, if the number is exceeded, then every nth item is removed to bring the count down. A more sophisticated mechanism may be available in the future.
    
    Returns:
    
    this, for chaining
    
    Status:
    Stable ICU 4.8.
  - buildImmutableIndex
```
public AlphabeticIndex.ImmutableIndex<V> buildImmutableIndex()
```
    Builds an immutable, thread-safe version of this instance, without data records.
    
    Returns:
    
    an immutable index instance
    
    Status:
    Stable ICU 51.
  - getBucketLabels
```
public List<String> getBucketLabels()
```
    Get the labels.
    
    Returns:
    
    The list of bucket labels, after processing.
    
    Status:
    Stable ICU 4.8.
  - getCollator
```
public RuleBasedCollator getCollator()
```
    Get a clone of the collator used internally. Note that for performance reasons, the clone is only done once, and then stored. The next time it is accessed, the same instance is returned.
    Don't use this method across threads if you are changing the settings on the collator, at least not without synchronizing.
    
    Returns:
    
    a clone of the collator used internally
    
    Status:
    Stable ICU 4.8.
  - addRecord
```
public AlphabeticIndex<V> addRecord(CharSequence name,
                                    V data)
```
    Add a record (name and data) to the index. The name will be used to sort the items into buckets, and to sort within the bucket. Two records may have the same name. When they do, the sort order is according to the order added: the first added comes first.
    
    Parameters:
    
    name - Name, such as a name
    
    data - Data, such as an address or link
    
    Returns:
    
    this, for chaining
    
    Status:
    Stable ICU 4.8.
  - getBucketIndex
```
public int getBucketIndex(CharSequence name)
```
    Get the bucket number for the given name. This routine permits callers to implement their own bucket handling mechanisms, including client-server handling. For example, when a new name is created on the client, it can ask the server for the bucket for that name, and the sortkey (using getCollator). Once the client has that information, it can put the name into the right bucket, and sort it within that bucket, without having access to the index or collator.
    Note that the bucket number (and sort key) are only valid for the settings of the current AlphabeticIndex; if those are changed, then the bucket number and sort key must be regenerated.
    
    Parameters:
    
    name - Name, such as a name
    
    Returns:
    
    the bucket index for the name
    
    Status:
    Stable ICU 4.8.
  - clearRecords
```
public AlphabeticIndex<V> clearRecords()
```
    Clear the index.
    
    Returns:
    
    this, for chaining
    
    Status:
    Stable ICU 4.8.
  - getBucketCount
```
public int getBucketCount()
```
    Return the number of buckets in the index. This will be the same as the number of labels, plus buckets for the underflow, overflow, and inflow(s).
    
    Returns:
    
    number of buckets
    
    Status:
    Stable ICU 4.8.
  - getRecordCount
```
public int getRecordCount()
```
    Return the number of records in the index: that is, the total number of distinct <name,data> pairs added with addRecord(...), over all the buckets.
    
    Returns:
    
    total number of records in buckets
    
    Status:
    Stable ICU 4.8.
  - iterator
```
public Iterator<AlphabeticIndex.Bucket<V>> iterator()
```
    Return an iterator over the buckets.
    
    Specified by:
    
    iterator in interface Iterable<AlphabeticIndex.Bucket<V>>
    
    Returns:
    
    iterator over buckets.
    
    Status:
    Stable ICU 4.8.
  - getFirstCharactersInScripts
```
@Deprecated
public List<String> getFirstCharactersInScripts()
```
    Deprecated. This API is ICU internal, only for testing.
    
    Return a list of the first character in each script. Only exposed for testing.
    
    Returns:
    
    list of first characters in each script
    
    Status:
    Internal. This API is ICU internal only.

Class AlphabeticIndex<V>

Direct Use

Client Support

Nested Class Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Methods inherited from interface java.lang.Iterable

Constructor Detail

AlphabeticIndex

AlphabeticIndex

AlphabeticIndex

Method Detail

addLabels

addLabels

addLabels

setOverflowLabel

getUnderflowLabel

setUnderflowLabel

getOverflowLabel

setInflowLabel

getInflowLabel

getMaxLabelCount

setMaxLabelCount

buildImmutableIndex

getBucketLabels

getCollator

addRecord

getBucketIndex

clearRecords

getBucketCount

getRecordCount

iterator

getFirstCharactersInScripts