// There are a few design constraints to consider
  // * We want to be responsive to small timeouts, unpark() has non trivial latency overheads (I
  //   have observed 12 micros on 64-bit linux systems to wake up a parked thread). So if the
  //   timeout is small we shouldn't park(). This needs to be traded off with the cpu overhead of
  //   spinning, so we use SPIN_THRESHOLD_NANOS which is what AbstractQueuedSynchronizer uses for
  //   similar purposes.

  // There are a few design constraints to consider
  // * We want to be responsive to small timeouts, unpark() has non trivial latency overheads (I
  //   have observed 12 micros on 64-bit linux systems to wake up a parked thread). So if the
  //   timeout is small we shouldn't park(). This needs to be traded off with the cpu overhead of
  //   spinning, so we use SPIN_THRESHOLD_NANOS which is what AbstractQueuedSynchronizer uses for
  //   similar purposes.

 * </ul>
 *
 * <p>Disadvantages compared to {@code long[]}:
 *
 * <ul>
 *   <li>Memory footprint has a fixed overhead (about 24 bytes per instance).
 *   <li><i>Some</i> construction use cases force the data to be copied (though several construction
 *       APIs are offered that don't).
 *   <li>Can't be passed directly to methods that expect {@code long[]} (though the most common
 *       utilities do have replacements here).

 * </ul>
 *
 * <p>Disadvantages compared to {@code int[]}:
 *
 * <ul>
 *   <li>Memory footprint has a fixed overhead (about 24 bytes per instance).
 *   <li><i>Some</i> construction use cases force the data to be copied (though several construction
 *       APIs are offered that don't).
 *   <li>Can't be passed directly to methods that expect {@code int[]} (though the most common
 *       utilities do have replacements here).

  }

  // 'test' to demonstrate some potentially ambiguous overloads.  This 'test' is kind of strange,
  // but essentially each line will be a call to a Preconditions method that, but for a documented
  // change would be a compiler error.
  // See http://docs.oracle.com/javase/specs/jls/se7/html/jls-15.html#jls-15.12.2 for the spec on
  // how javac selects overloads
  @SuppressWarnings("null")
  public void overloadSelection() {

  }

  // 'test' to demonstrate some potentially ambiguous overloads.  This 'test' is kind of strange,
  // but essentially each line will be a call to a Preconditions method that, but for a documented
  // change would be a compiler error.
  // See http://docs.oracle.com/javase/specs/jls/se7/html/jls-15.html#jls-15.12.2 for the spec on
  // how javac selects overloads
  @SuppressWarnings("null")
  public void overloadSelection() {

- **Memory efficient** - Specialized collections like `LruHashMap` and `ArrayMap` for memory-conscious applications
- **Java 21 features** - Switch expressions and pattern matching for reduced overhead

## 🧪 Building and Testing

### Development Setup
```bash
# Clone the repository
git clone https://github.com/codelibs/corelib.git
cd corelib

# Compile the project
mvn clean compile

import java.util.concurrent.atomic.AtomicInteger;
import junit.framework.TestCase;
import org.jspecify.annotations.NullUnmarked;

/** Unit tests for CacheBuilder. */
@GwtCompatible
// We are intentionally testing the TimeUnit overloads, too.
@SuppressWarnings("LongTimeUnit_ExpireAfterWrite_Seconds")
@NullUnmarked
public class CacheBuilderTest extends TestCase {

  public void testNewBuilder() {

import java.util.concurrent.atomic.AtomicInteger;
import junit.framework.TestCase;
import org.jspecify.annotations.NullUnmarked;

/** Unit tests for CacheBuilder. */
@GwtCompatible
// We are intentionally testing the TimeUnit overloads, too.
@SuppressWarnings("LongTimeUnit_ExpireAfterWrite_Seconds")
@NullUnmarked
public class CacheBuilderTest extends TestCase {

  public void testNewBuilder() {