TrieIterator

Class Overview

Class enabling iteration of the values in a Trie.

Result of each iteration contains the interval of codepoints that have the same value type and the value type itself.

The comparison of each codepoint value is done via extract(), which the default implementation is to return the value as it is.

Method extract() can be overwritten to perform manipulations on codepoint values in order to perform specialized comparison.

TrieIterator is designed to be a generic iterator for the CharTrie and the IntTrie, hence to accommodate both types of data, the return result will be in terms of int (32 bit) values.

See com.ibm.icu.text.UCharacterTypeIterator for examples of use.

Notes for porting utrie_enum from icu4c to icu4j:
Internally, icu4c's utrie_enum performs all iterations in its body. In Java sense, the caller will have to pass a object with a callback function UTrieEnumRange(const void *context, UChar32 start, UChar32 limit, uint32_t value) into utrie_enum. utrie_enum will then find ranges of codepoints with the same value as determined by UTrieEnumValue(const void *context, uint32_t value). for each range, utrie_enum calls the callback function to perform a task. In this way, icu4c performs the iteration within utrie_enum. To follow the JDK model, icu4j is slightly different from icu4c. Instead of requesting the caller to implement an object for a callback. The caller will have to implement a subclass of TrieIterator, fleshing out the method extract(int) (equivalent to UTrieEnumValue). Independent of icu4j, the caller will have to code his own iteration and flesh out the task (equivalent to UTrieEnumRange) to be performed in the iteration loop.

There are basically 3 usage scenarios for porting:

1) UTrieEnumValue is the only implemented callback then just implement a subclass of TrieIterator and override the extract(int) method. The extract(int) method is analogus to UTrieEnumValue callback.

2) UTrieEnumValue and UTrieEnumRange both are implemented then implement a subclass of TrieIterator, override the extract method and iterate, e.g

utrie_enum(&normTrie, _enumPropertyStartsValue, _enumPropertyStartsRange, set);
In Java :

 class TrieIteratorImpl extends TrieIterator{
     public TrieIteratorImpl(Trie data){
         super(data);
     }
     public int extract(int value){
         // port the implementation of _enumPropertyStartsValue here
     }
 }
 ....
 TrieIterator fcdIter  = new TrieIteratorImpl(fcdTrieImpl.fcdTrie);
 while(fcdIter.next(result)) {
     // port the implementation of _enumPropertyStartsRange
 }
 

3) UTrieEnumRange is the only implemented callback then just implement the while loop, when utrie_enum is called

 // utrie_enum(&fcdTrie, NULL, _enumPropertyStartsRange, set);
 TrieIterator fcdIter  = new TrieIterator(fcdTrieImpl.fcdTrie);
 while(fcdIter.next(result)){
     set.add(result.start);
 }
 

Summary

[Expand] Inherited Methods
From class java.lang.Object Object clone() Creates and returns a copy of this object. boolean equals(Object obj) Indicates whether some other object is "equal to" this one. void finalize() Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. final Class<?> getClass() Returns the runtime class of this Object. int hashCode() Returns a hash code value for the object. final void notify() Wakes up a single thread that is waiting on this object's monitor. final void notifyAll() Wakes up all threads that are waiting on this object's monitor. String toString() Returns a string representation of the object. final void wait() Causes the current thread to wait until another thread invokes the notify() method or the notifyAll() method for this object. final void wait(long timeout, int nanos) Causes the current thread to wait until another thread invokes the notify() method or the notifyAll() method for this object, or some other thread interrupts the current thread, or a certain amount of real time has elapsed. final void wait(long timeout) Causes the current thread to wait until either another thread invokes the notify() method or the notifyAll() method for this object, or a specified amount of time has elapsed.
From interface sun.text.normalizer.RangeValueIterator abstract boolean next(RangeValueIterator.Element element) Gets the next maximal result range with a common value and returns true if we are not at the end of the iteration, false otherwise. abstract void reset() Resets the iterator to the beginning of the iteration.