1 /*
2  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
3  *
4  * This code is free software; you can redistribute it and/or modify it
5  * under the terms of the GNU General Public License version 2 only, as
6  * published by the Free Software Foundation.  Oracle designates this
7  * particular file as subject to the "Classpath" exception as provided
8  * by Oracle in the LICENSE file that accompanied this code.
9  *
10  * This code is distributed in the hope that it will be useful, but WITHOUT
11  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
13  * version 2 for more details (a copy is included in the LICENSE file that
14  * accompanied this code).
15  *
16  * You should have received a copy of the GNU General Public License version
17  * 2 along with this work; if not, write to the Free Software Foundation,
18  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19  *
20  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21  * or visit www.oracle.com if you need additional information or have any
22  * questions.
23  */
24 
25 /*
26  * This file is available under and governed by the GNU General Public
27  * License version 2 only, as published by the Free Software Foundation.
28  * However, the following notice accompanied the original version of this
29  * file:
30  *
31  * Written by Martin Buchholz with assistance from members of JCP
32  * JSR-166 Expert Group and released to the public domain, as
33  * explained at http://creativecommons.org/publicdomain/zero/1.0/
34  */
35 
36 package java.util.concurrent;
37 
38 import java.util.Collection;
39 
40 /** Shared implementation code for java.util.concurrent. */
41 class Helpers {
Helpers()42     private Helpers() {}                // non-instantiable
43 
44     /**
45      * An implementation of Collection.toString() suitable for classes
46      * with locks.  Instead of holding a lock for the entire duration of
47      * toString(), or acquiring a lock for each call to Iterator.next(),
48      * we hold the lock only during the call to toArray() (less
49      * disruptive to other threads accessing the collection) and follows
50      * the maxim "Never call foreign code while holding a lock".
51      */
collectionToString(Collection<?> c)52     static String collectionToString(Collection<?> c) {
53         final Object[] a = c.toArray();
54         final int size = a.length;
55         if (size == 0)
56             return "[]";
57         int charLength = 0;
58 
59         // Replace every array element with its string representation
60         for (int i = 0; i < size; i++) {
61             Object e = a[i];
62             // Extreme compatibility with AbstractCollection.toString()
63             String s = (e == c) ? "(this Collection)" : objectToString(e);
64             a[i] = s;
65             charLength += s.length();
66         }
67 
68         return toString(a, size, charLength);
69     }
70 
71     /**
72      * Like Arrays.toString(), but caller guarantees that size > 0,
73      * each element with index 0 <= i < size is a non-null String,
74      * and charLength is the sum of the lengths of the input Strings.
75      */
toString(Object[] a, int size, int charLength)76     static String toString(Object[] a, int size, int charLength) {
77         // assert a != null;
78         // assert size > 0;
79 
80         // Copy each string into a perfectly sized char[]
81         // Length of [ , , , ] == 2 * size
82         final char[] chars = new char[charLength + 2 * size];
83         chars[0] = '[';
84         int j = 1;
85         for (int i = 0; i < size; i++) {
86             if (i > 0) {
87                 chars[j++] = ',';
88                 chars[j++] = ' ';
89             }
90             String s = (String) a[i];
91             int len = s.length();
92             s.getChars(0, len, chars, j);
93             j += len;
94         }
95         chars[j] = ']';
96         // assert j == chars.length - 1;
97         return new String(chars);
98     }
99 
100     /** Optimized form of: key + "=" + val */
mapEntryToString(Object key, Object val)101     static String mapEntryToString(Object key, Object val) {
102         final String k, v;
103         final int klen, vlen;
104         final char[] chars =
105             new char[(klen = (k = objectToString(key)).length()) +
106                      (vlen = (v = objectToString(val)).length()) + 1];
107         k.getChars(0, klen, chars, 0);
108         chars[klen] = '=';
109         v.getChars(0, vlen, chars, klen + 1);
110         return new String(chars);
111     }
112 
objectToString(Object x)113     private static String objectToString(Object x) {
114         // Extreme compatibility with StringBuilder.append(null)
115         String s;
116         return (x == null || (s = x.toString()) == null) ? "null" : s;
117     }
118 }
119