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