System.setProperty("var2", "value2");

        String value = "${var1}-${var2}";
        assertEquals("value1-value2", ResourceUtil.resolve(value));

        // Test nested-like patterns (but not actual nesting)
        value = "${var1${var2}}"; // The ${var2} part gets replaced first
        assertEquals("${var1value2}", ResourceUtil.resolve(value));

 * each event pair are used to link the event in case of concurrent or repeated events e.g.
 * `dnsStart(call, domainName)` → `dnsEnd(call, domainName, inetAddressList)`.
 *
 * Events are typically nested with this structure:
 *
 *  * call ([callStart], [callEnd], [callFailed])
 *    * proxy selection ([proxySelectStart], [proxySelectEnd])
 *    * dns ([dnsStart], [dnsEnd])

        Map<String, Object> doc = new HashMap<>();

        Map<String, Object> nestedMap = new HashMap<>();
        nestedMap.put("nestedKey", "nestedValue");
        doc.put("nested", nestedMap);

        List<Map<String, Object>> listOfMaps = new ArrayList<>();
        listOfMaps.add(nestedMap);
        doc.put("listOfMaps", listOfMaps);

import java.util.NoSuchElementException;
import java.util.Set;
import java.util.SortedSet;
import junit.framework.TestCase;
import org.jspecify.annotations.NullUnmarked;

/**
 * Class that contains nested abstract tests for filtered collection views, along with their
 * implementation helpers.
 *
 * @author Louis Wasserman
 */
/*

     * is the only one in use, but if we encounter nested concatenations, we start a deque of
     * meta-iterators rather than letting the nesting get arbitrarily deep.  This keeps each
     * operation O(1).
     */

    private @Nullable Iterator<? extends Iterator<? extends T>> topMetaIterator;

    // Only becomes nonnull if we encounter nested concatenations.

 * Immutable} type provides the static operations you need to obtain instances of that type. These
 * usually include:
 *
 * <ul>
 *   <li>Static methods named {@code of}, accepting an explicit list of elements or entries.
 *   <li>Static methods named {@code copyOf} (or {@code copyOfSorted}), accepting an existing
 *       collection whose contents should be copied.

 * Benchmarks (as of December 2011) show that:
 *
 * <ul>
 *   <li>for an unnested {@code lock()} and {@code unlock()}, a cycle detecting lock takes 38ns as
 *       opposed to the 24ns taken by a plain lock.
 *   <li>for nested locking, the cost increases with the depth of the nesting:
 *       <ul>
 *         <li>2 levels: average of 64ns per lock()/unlock()

    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <!--
    Some tests need reflective access to the internals of these packages. It is only the
    tests themselves and not the code being tested that needs that access, though there's no
    obvious way to ensure that.

    We could consider arranging things so that only the tests we know need this would get
    the add-opens. Right now that doesn't seem worth the effort, though.
    -->

    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <!--
    Some tests need reflective access to the internals of these packages. It is only the
    tests themselves and not the code being tested that needs that access, though there's no
    obvious way to ensure that.

    We could consider arranging things so that only the tests we know need this would get
    the add-opens. Right now that doesn't seem worth the effort, though.
    -->

    Object writeReplace() {
    return super.writeReplace();
  }

  // This class is never actually serialized directly, but we have to make the
  // warning go away (and suppressing would suppress for all nested classes too)
  @GwtIncompatible @J2ktIncompatible private static final long serialVersionUID = 0;