1 /*
2 * Copyright (c) 2012, 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25 package java.util;
26
27 import java.io.Serializable;
28 import java.util.function.BinaryOperator;
29 import java.util.function.Function;
30 import java.util.function.ToDoubleFunction;
31 import java.util.function.ToIntFunction;
32 import java.util.function.ToLongFunction;
33
34 /**
35 * Package private supporting class for {@link Comparator}.
36 */
37 class Comparators {
38 private Comparators() {
39 throw new AssertionError("no instances");
40 }
41
42 /**
43 * Compares {@link Comparable} objects in natural order.
44 *
45 * @see Comparable
46 */
47 enum NaturalOrderComparator implements Comparator<Comparable<Object>> {
48 INSTANCE;
49
50 @Override
51 public int compare(Comparable<Object> c1, Comparable<Object> c2) {
52 return c1.compareTo(c2);
53 }
54
55 @Override
56 public Comparator<Comparable<Object>> reversed() {
57 return Comparator.reverseOrder();
58 }
59 }
60
61 /**
62 * Null-friendly comparators
63 */
64 static final class NullComparator<T> implements Comparator<T>, Serializable {
65 private static final long serialVersionUID = -7569533591570686392L;
66 private final boolean nullFirst;
67 // if null, non-null Ts are considered equal
68 private final Comparator<T> real;
69
70 @SuppressWarnings("unchecked")
71 NullComparator(boolean nullFirst, Comparator<? super T> real) {
72 this.nullFirst = nullFirst;
73 this.real = (Comparator<T>) real;
74 }
75
76 @Override
77 public int compare(T a, T b) {
78 if (a == null) {
79 return (b == null) ? 0 : (nullFirst ? -1 : 1);
80 } else if (b == null) {
81 return nullFirst ? 1: -1;
82 } else {
83 return (real == null) ? 0 : real.compare(a, b);
84 }
85 }
86
87 @Override
88 public Comparator<T> thenComparing(Comparator<? super T> other) {
89 Objects.requireNonNull(other);
90 return new NullComparator<>(nullFirst, real == null ? other : real.thenComparing(other));
91 }
92
93 @Override
94 public Comparator<T> reversed() {
95 return new NullComparator<>(!nullFirst, real == null ? null : real.reversed());
96 }
97 }
98
99 /**
100 * Compares char sequences, taking into account their numeric part if one exists.
101 *
102 * @see Comparator.comparingNumerically()
103 * @see Comparator.comparingNumericallyLeadingZerosFirst()
104 */
105 static class NumericComparator<T extends CharSequence> implements Comparator<T>, Serializable {
106
107 private static final long serialVersionUID = 0x77164074580FAC97L;
108
109 static final Comparator<?> INSTANCE_LEADING_ZEROS_FIRST_NATURAL =
110 new NumericComparator<CharSequence>(true)
111 {
112 @Override
113 @SuppressWarnings("unchecked")
114 public Comparator<CharSequence> reversed() {
115 return (Comparator<CharSequence>)INSTANCE_LEADING_ZEROS_FIRST_REVERSED;
116 }
117 };
118
119 static final Comparator<?> INSTANCE_LEADING_ZEROS_FIRST_REVERSED =
120 new NumericComparator<CharSequence>(true)
121 {
122 @Override
123 public int compare(CharSequence o1, CharSequence o2) {
124 return super.compare(o2, o1);
125 }
126
127 @Override
128 @SuppressWarnings("unchecked")
129 public Comparator<CharSequence> reversed() {
130 return (Comparator<CharSequence>)INSTANCE_LEADING_ZEROS_FIRST_NATURAL;
131 }
132 };
133
134 static final Comparator<?> INSTANCE_LEADING_ZEROS_LAST_NATURAL =
135 new NumericComparator<CharSequence>(false)
136 {
137 @Override
138 @SuppressWarnings("unchecked")
139 public Comparator<CharSequence> reversed() {
140 return (Comparator<CharSequence>)INSTANCE_LEADING_ZEROS_LAST_REVERSED;
141 }
142 };
143
144 static final Comparator<?> INSTANCE_LEADING_ZEROS_LAST_REVERSED =
145 new NumericComparator<CharSequence>(false)
146 {
147 @Override
148 public int compare(CharSequence o1, CharSequence o2) {
149 return super.compare(o2, o1);
150 }
151
152 @Override
153 @SuppressWarnings("unchecked")
154 public Comparator<CharSequence> reversed() {
155 return (Comparator<CharSequence>)INSTANCE_LEADING_ZEROS_LAST_NATURAL;
156 }
157 };
158
159 /**
160 * If true, the string representation of a number with
161 * more leading zeros will be treated as smaller.
162 * E.g.: "0001" < "001" < "1".
163 */
164 private final boolean leadingZerosFirst;
165
166 /**
167 * Constructs a new comparator with possibility to specify
168 * how it should deal with leading zeros in numbers.
169 *
170 * @param leadingZerosFirst if {@code true}, numbers with
171 * more leading zeros are treated as smaller.
172 */
173 private NumericComparator(boolean leadingZerosFirst) {
174 this.leadingZerosFirst = leadingZerosFirst;
175 }
176
177 /**
178 * Counts how many consequtive characters in the string {@code o}
179 * are digits, starting from the position {@code from}.
180 */
181 private int countDigits(CharSequence o, int from) {
182 for (int i = from, len = o.length(); ; ++i) {
183 if (i == len || !Character.isDigit(o.charAt(i))) {
184 return i - from;
185 }
186 }
187 }
188
189 /**
190 * Checks if all {@code cnt} chars of the sequence {@code o},
191 * starting with {@code pos} are zeros.
192 *
193 * @param pos position of the first digit of numeric part.
194 * @param cnt number of digits to check; must be > 0.
195 *
196 * @return {@code true} if the numeric part of the string {@code o}
197 * can be reduced in length by {@code cnt} without changing its
198 * numerical value.
199 */
200 private boolean skipLeadingZeros(CharSequence o, int pos, int cnt) {
201 do {
202 if (Character.digit(o.charAt(pos++), 10) != 0) {
203 // Leading digit of numeric part of o isn't zero
204 return false;
205 }
206 } while (--cnt > 0);
207 return true;
208 }
209
210 @Override
211 public int compare(T o1, T o2) {
212 int minLen = Math.min(o1.length(), o2.length());
213 int numStart1 = 0;
214 int index = 0;
215 int res0 = 0;
216
217 // Skip common prefix of the arguments
218 char ch;
219 while (index < minLen &&
220 (res0 = Character.compare(ch = o1.charAt(index),
221 o2.charAt(index))) == 0) {
222 ++index;
223 if (!Character.isDigit(ch)) {
224 numStart1 = index;
225 }
226 }
227
228 int numLen1 = index - numStart1;
229 if (numLen1 > 0 ||
230 (index < minLen &&
231 Character.isDigit(o1.charAt(index)) &&
232 Character.isDigit(o2.charAt(index))))
233 {
234 // The difference is inside or at the boundary of
235 // numerical part
236 int numLen2 = numLen1;
237 int numStart2 = numStart1;
238
239 numLen1 += countDigits(o1, index);
240 numLen2 += countDigits(o2, index);
241
242 int diffNumLen = numLen2 - numLen1;
243
244 if (diffNumLen > 0) {
245 if (!skipLeadingZeros(o2, numStart2, diffNumLen)) {
246 // Length of numeric part of o2 is greater
247 return -1;
248 }
249 numStart2 += diffNumLen;
250 numLen2 = numLen1;
251 } else if (diffNumLen < 0) {
252 if (!skipLeadingZeros(o1, numStart1, -diffNumLen)) {
253 // Length of numeric part of o1 is greater
254 return 1;
255 }
256 numStart1 -= diffNumLen;
257 numLen1 = numLen2;
258 }
259
260 // Numeric parts are of the same length, so they can
261 // be compared literally
262 while (numLen1-- > 0) {
263 int res1 = Character.compare(o1.charAt(numStart1++),
264 o2.charAt(numStart2++));
265 if (res1 != 0) {
266 return res1;
267 }
268 }
269
270 // Numeric parts are numerically equal
271 if (diffNumLen != 0) {
272 // If leadingZerosFirst == true, treat the number
273 // with more leading zeros as smaller
274 return (leadingZerosFirst ^ (diffNumLen > 0)) ? -1 : 1;
275 }
276 }
277
278 // Otherwise, compare literally
279 return (index < o1.length())
280 ? ((index < o2.length()) ? res0 : 1)
281 : ((index < o2.length()) ? -1 : 0);
282 }
283 }
284 }