* cross-language compatibility. For other use cases, prefer {@link #hashUnencodedChars}, which is
   * faster, produces the same output across Java releases, and hashes every {@code char} in the
   * input, even if some are invalid.
   */
  HashCode hashString(CharSequence input, Charset charset);

  /**

 *
 * <ul>
 *   <li>Each lock adds (and removes) itself to/from a ThreadLocal Set of acquired locks when the
 *       Thread acquires its first hold (and releases its last remaining hold).
 *   <li>Before the lock is acquired, the lock is checked against the current set of acquired
 *       locks---to each of the acquired locks, an edge from the soon-to-be-acquired lock is either

/**
 * A rate limiter. Conceptually, a rate limiter distributes permits at a configurable rate. Each
 * {@link #acquire()} blocks if necessary until a permit is available, and then takes it. Once
 * acquired, permits need not be released.
 *
 * <p>{@code RateLimiter} is safe for concurrent use: It will restrict the total rate of calls from
 * all threads. Note, however, that it does not guarantee fairness.
 *

/*
 * Written by Doug Lea and 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/
 */

/*
 * Source:
 * http://gee.cs.oswego.edu/cgi-bin/viewcvs.cgi/jsr166/src/test/tck-jsr166e/AtomicDoubleArrayTest.java?revision=1.13
 * (Modified to adapt to guava coding conventions)
 */

package com.google.common.util.concurrent;

/*
 * Written by Doug Lea and 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/
 */

/*
 * Source:
 * http://gee.cs.oswego.edu/cgi-bin/viewcvs.cgi/jsr166/src/test/tck-jsr166e/AtomicDoubleArrayTest.java?revision=1.13
 * (Modified to adapt to guava coding conventions)
 */

package com.google.common.util.concurrent;

/*
 * Written by Doug Lea 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/
 * Other contributors include Andrew Wright, Jeffrey Hayes,
 * Pat Fisher, Mike Judd.
 */

/*
 * Source:
 * http://gee.cs.oswego.edu/cgi-bin/viewcvs.cgi/jsr166/src/test/tck/JSR166TestCase.java?revision=1.90

   * @since 20.0
   */
  public static long floorPowerOfTwo(long x) {
    checkPositive("x", x);

    // Long.highestOneBit was buggy on GWT.  We've fixed it, but I'm not certain when the fix will
    // be released.
    return 1L << ((Long.SIZE - 1) - Long.numberOfLeadingZeros(x));
  }

  /**
   * Returns {@code true} if {@code x} represents a power of two.
   *

/*
 * Written by Doug Lea 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/
 */

/*
 * Source:
 * http://gee.cs.oswego.edu/cgi-bin/viewcvs.cgi/jsr166/src/jsr166e/Striped64.java?revision=1.9
 */

package com.google.common.cache;

import com.google.common.annotations.GwtIncompatible;
import java.util.Random;

    }
  }

  /** Returns a serializable converter that always converts or reverses an object to itself. */
  @SuppressWarnings("unchecked") // implementation is "fully variant"
  public static <T> Converter<T, T> identity() {
    return (IdentityConverter<T>) IdentityConverter.INSTANCE;
  }

  /**
   * A converter that always converts or reverses an object to itself. Note that T is now a
   * "pass-through type".
   */

/*
 * Written by Doug Lea 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/
 * Other contributors include Andrew Wright, Jeffrey Hayes,
 * Pat Fisher, Mike Judd.
 */

/*
 * Source:
 * http://gee.cs.oswego.edu/cgi-bin/viewcvs.cgi/jsr166/src/test/tck/JSR166TestCase.java?revision=1.90