Class CollationKey
- java.lang.Object
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- java.text.CollationKey
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- All Implemented Interfaces:
- Comparable<CollationKey>
public abstract class CollationKey extends Object implements Comparable<CollationKey>
ACollationKeyrepresents aStringunder the rules of a specificCollatorobject. Comparing twoCollationKeys returns the relative order of theStrings they represent. UsingCollationKeys to compareStrings is generally faster than usingCollator.compare. Thus, when theStrings must be compared multiple times, for example when sorting a list ofStrings. It's more efficient to useCollationKeys.You can not create
CollationKeys directly. Rather, generate them by callingCollator.getCollationKey. You can only compareCollationKeys generated from the sameCollatorobject.Generating a
CollationKeyfor aStringinvolves examining the entireStringand converting it to series of bits that can be compared bitwise. This allows fast comparisons once the keys are generated. The cost of generating keys is recouped in faster comparisons whenStrings need to be compared many times. On the other hand, the result of a comparison is often determined by the first couple of characters of eachString.Collator.compareexamines only as many characters as it needs which allows it to be faster when doing single comparisons.The following example shows how
CollationKeys might be used to sort a list ofStrings.// Create an array of CollationKeys for the Strings to be sorted. Collator myCollator = Collator.getInstance(); CollationKey[] keys = new CollationKey[3]; keys[0] = myCollator.getCollationKey("Tom"); keys[1] = myCollator.getCollationKey("Dick"); keys[2] = myCollator.getCollationKey("Harry"); sort(keys); //... // Inside body of sort routine, compare keys this way if (keys[i].compareTo(keys[j]) > 0) // swap keys[i] and keys[j] //... // Finally, when we've returned from sort. System.out.println(keys[0].getSourceString()); System.out.println(keys[1].getSourceString()); System.out.println(keys[2].getSourceString());- See Also:
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Collator,RuleBasedCollator
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Constructor Summary
Constructors Modifier Constructor and Description protectedCollationKey(String source)CollationKey constructor.
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Method Summary
All Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method and Description abstract intcompareTo(CollationKey target)Compare this CollationKey to the target CollationKey.StringgetSourceString()Returns the String that this CollationKey represents.abstract byte[]toByteArray()Converts the CollationKey to a sequence of bits.
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Constructor Detail
CollationKey
protected CollationKey(String source)
CollationKey constructor.- Parameters:
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source- the source string - Throws:
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NullPointerException- ifsourceis null - Since:
- 1.6
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Method Detail
compareTo
public abstract int compareTo(CollationKey target)
Compare this CollationKey to the target CollationKey. The collation rules of the Collator object which created these keys are applied. Note: CollationKeys created by different Collators can not be compared.- Specified by:
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compareToin interfaceComparable<CollationKey> - Parameters:
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target- target CollationKey - Returns:
- Returns an integer value. Value is less than zero if this is less than target, value is zero if this and target are equal and value is greater than zero if this is greater than target.
- See Also:
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Collator.compare(java.lang.String, java.lang.String)
getSourceString
public String getSourceString()
Returns the String that this CollationKey represents.- Returns:
- the source string of this CollationKey
toByteArray
public abstract byte[] toByteArray()
Converts the CollationKey to a sequence of bits. If two CollationKeys could be legitimately compared, then one could compare the byte arrays for each of those keys to obtain the same result. Byte arrays are organized most significant byte first.- Returns:
- a byte array representation of the CollationKey
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