jdk/src/share/classes/java/text/CollationKey.java
changeset 2 90ce3da70b43
child 5506 202f599c92aa
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/share/classes/java/text/CollationKey.java	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,145 @@
+/*
+ * Copyright 1997-2005 Sun Microsystems, Inc.  All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Sun designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Sun in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ */
+
+/*
+ * (C) Copyright Taligent, Inc. 1996 - All Rights Reserved
+ * (C) Copyright IBM Corp. 1996 - All Rights Reserved
+ *
+ *   The original version of this source code and documentation is copyrighted
+ * and owned by Taligent, Inc., a wholly-owned subsidiary of IBM. These
+ * materials are provided under terms of a License Agreement between Taligent
+ * and Sun. This technology is protected by multiple US and International
+ * patents. This notice and attribution to Taligent may not be removed.
+ *   Taligent is a registered trademark of Taligent, Inc.
+ *
+ */
+
+package java.text;
+
+/**
+ * A <code>CollationKey</code> represents a <code>String</code> under the
+ * rules of a specific <code>Collator</code> object. Comparing two
+ * <code>CollationKey</code>s returns the relative order of the
+ * <code>String</code>s they represent. Using <code>CollationKey</code>s
+ * to compare <code>String</code>s is generally faster than using
+ * <code>Collator.compare</code>. Thus, when the <code>String</code>s
+ * must be compared multiple times, for example when sorting a list
+ * of <code>String</code>s. It's more efficient to use <code>CollationKey</code>s.
+ *
+ * <p>
+ * You can not create <code>CollationKey</code>s directly. Rather,
+ * generate them by calling <code>Collator.getCollationKey</code>.
+ * You can only compare <code>CollationKey</code>s generated from
+ * the same <code>Collator</code> object.
+ *
+ * <p>
+ * Generating a <code>CollationKey</code> for a <code>String</code>
+ * involves examining the entire <code>String</code>
+ * and 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 when <code>String</code>s 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 each <code>String</code>.
+ * <code>Collator.compare</code> examines only as many characters as it needs which
+ * allows it to be faster when doing single comparisons.
+ * <p>
+ * The following example shows how <code>CollationKey</code>s might be used
+ * to sort a list of <code>String</code>s.
+ * <blockquote>
+ * <pre>
+ * // 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 );
+ * <br>
+ * //...
+ * <br>
+ * // Inside body of sort routine, compare keys this way
+ * if( keys[i].compareTo( keys[j] ) > 0 )
+ *    // swap keys[i] and keys[j]
+ * <br>
+ * //...
+ * <br>
+ * // 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() );
+ * </pre>
+ * </blockquote>
+ *
+ * @see          Collator
+ * @see          RuleBasedCollator
+ * @author       Helena Shih
+ */
+
+public abstract class CollationKey implements Comparable<CollationKey> {
+    /**
+     * Compare this CollationKey to the target CollationKey. The collation rules of the
+     * Collator object which created these keys are applied. <strong>Note:</strong>
+     * CollationKeys created by different Collators can not be compared.
+     * @param target target CollationKey
+     * @return 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 java.text.Collator#compare
+     */
+    abstract public int compareTo(CollationKey target);
+
+    /**
+     * Returns the String that this CollationKey represents.
+     */
+    public String getSourceString() {
+        return source;
+    }
+
+
+    /**
+     * 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.
+     */
+    abstract public byte[] toByteArray();
+
+
+  /**
+   * CollationKey constructor.
+   *
+   * @param source - the source string.
+   * @exception NullPointerException if <code>source</code> is null.
+   * @since 1.6
+   */
+    protected CollationKey(String source) {
+        if (source==null){
+            throw new NullPointerException();
+        }
+        this.source = source;
+    }
+
+    final private String source;
+}