* iterator's next element and pass it to the reference iterator through this method so it can
     * return the same element. This enables the assertion to pass and the reference iterator to
     * properly update its state.
     */
    void promoteToNext(E e) {
      if (nextElements.remove(e)) {
        nextElements.push(e);
      } else {

 * </pre>
 *
 * <h3>Option 2: Set individual SP URLs</h3>
 * <pre>
 * # SP Entity ID (Audience URI in IdP)
 * saml.sp.entityid=https://your-fess-server.example.com/sso/metadata
 *
 * # Assertion Consumer Service URL
 * saml.sp.assertion_consumer_service.url=https://your-fess-server.example.com/sso/
 *
 * # Single Logout Service URL
 * saml.sp.single_logout_service.url=https://your-fess-server.example.com/sso/logout

}
```

## 🏗️ Architecture & Design Patterns

### Core Design Principles
CoreLib follows a **utility-class pattern** where most functionality is exposed through static methods:

- **Assertion-based validation** - All methods validate inputs using `AssertionUtil.assertArgumentNotNull()` and `AssertionUtil.assertArgumentNotEmpty()`

import java.util.List;
import java.util.Map.Entry;
import java.util.Set;
import org.jspecify.annotations.NullMarked;
import org.jspecify.annotations.Nullable;

/**
 * A series of tests that support asserting that collections cannot be modified, either through
 * direct or indirect means.
 *
 * @author Robert Konigsberg
 */
@GwtCompatible
@NullMarked
public class UnmodifiableCollectionTests {

first time You have received notice of non-compliance with this License
from such Contributor, and You become compliant prior to 30 days after
Your receipt of the notice.

5.2. If You initiate litigation against any entity by asserting a patent
infringement claim (excluding declaratory judgment actions,
counter-claims, and cross-claims) alleging that a Contributor Version
directly or indirectly infringes any patent, then the rights granted to

          }
        }
      }
      return this;
    }

    /**
     * Tests {@link Object#equals} and {@link Object#hashCode} against the return values of the
     * static methods, by asserting that when equal parameters are passed to the same static method,
     * the return value should also be equal; and vice versa.
     *
     * <p>Test fails if default value cannot be determined for a constructor or factory method

    waiter.join();
    future.set(null);
    poller.join();
  }

  public void testToString_allUnique() throws Exception {
    // Two futures should not have the same toString, to avoid people asserting on it
    assertThat(SettableFuture.create().toString()).isNotEqualTo(SettableFuture.create().toString());
  }

  public void testToString_oom() throws Exception {

    waiter.join();
    future.set(null);
    poller.join();
  }

  public void testToString_allUnique() throws Exception {
    // Two futures should not have the same toString, to avoid people asserting on it
    assertThat(SettableFuture.create().toString()).isNotEqualTo(SettableFuture.create().toString());
  }

  public void testToString_oom() throws Exception {