/*
 * 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.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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/*
 * This file is available under and governed by the GNU General Public
 * License version 2 only, as published by the Free Software Foundation.
 * However, the following notice accompanied the original version of this
 * file:
 *
 * Written by Martin Buchholz with assistance from members of JCP
 * JSR-166 Expert Group and released to the public domain, as
 * explained at http://creativecommons.org/publicdomain/zero/1.0/
 */

package java.util.concurrent;

import java.util.Collection;

Shared implementation code for java.util.concurrent. /** Shared implementation code for java.util.concurrent. */
class Helpers {
    private Helpers() {}                // non-instantiable

    
An implementation of Collection.toString() suitable for classes
with locks.  Instead of holding a lock for the entire duration of
toString(), or acquiring a lock for each call to Iterator.next(),
we hold the lock only during the call to toArray() (less
disruptive to other threads accessing the collection) and follows
the maxim "Never call foreign code while holding a lock".
/**
     * An implementation of Collection.toString() suitable for classes
     * with locks.  Instead of holding a lock for the entire duration of
     * toString(), or acquiring a lock for each call to Iterator.next(),
     * we hold the lock only during the call to toArray() (less
     * disruptive to other threads accessing the collection) and follows
     * the maxim "Never call foreign code while holding a lock".
     */
    static String collectionToString(Collection<?> c) {
        final Object[] a = c.toArray();
        final int size = a.length;
        if (size == 0)
            return "[]";
        int charLength = 0;

        // Replace every array element with its string representation
        for (int i = 0; i < size; i++) {
            Object e = a[i];
            // Extreme compatibility with AbstractCollection.toString()
            String s = (e == c) ? "(this Collection)" : objectToString(e);
            a[i] = s;
            charLength += s.length();
        }

        return toString(a, size, charLength);
    }

    
Like Arrays.toString(), but caller guarantees that size > 0,
each element with index 0 <= i < size is a non-null String,
and charLength is the sum of the lengths of the input Strings.
/**
     * Like Arrays.toString(), but caller guarantees that size > 0,
     * each element with index 0 <= i < size is a non-null String,
     * and charLength is the sum of the lengths of the input Strings.
     */
    static String toString(Object[] a, int size, int charLength) {
        // assert a != null;
        // assert size > 0;

        // Copy each string into a perfectly sized char[]
        // Length of [ , , , ] == 2 * size
        final char[] chars = new char[charLength + 2 * size];
        chars[0] = '[';
        int j = 1;
        for (int i = 0; i < size; i++) {
            if (i > 0) {
                chars[j++] = ',';
                chars[j++] = ' ';
            }
            String s = (String) a[i];
            int len = s.length();
            s.getChars(0, len, chars, j);
            j += len;
        }
        chars[j] = ']';
        // assert j == chars.length - 1;
        return new String(chars);
    }

    
Optimized form of: key + "=" + val /** Optimized form of: key + "=" + val */
    static String mapEntryToString(Object key, Object val) {
        final String k, v;
        final int klen, vlen;
        final char[] chars =
            new char[(klen = (k = objectToString(key)).length()) +
                     (vlen = (v = objectToString(val)).length()) + 1];
        k.getChars(0, klen, chars, 0);
        chars[klen] = '=';
        v.getChars(0, vlen, chars, klen + 1);
        return new String(chars);
    }

    private static String objectToString(Object x) {
        // Extreme compatibility with StringBuilder.append(null)
        String s;
        return (x == null || (s = x.toString()) == null) ? "null" : s;
    }
}