* governing permissions and limitations under the License.
 */
package org.codelibs.core.lang;

import static org.hamcrest.CoreMatchers.is;
import static org.hamcrest.CoreMatchers.nullValue;
import static org.junit.Assert.assertSame;
import static org.junit.Assert.assertThat;

import org.junit.Test;

/**
 * @author wyukawa
 *
 */
public class ObjectUtilTest {

    /**

 */
package org.codelibs.core.lang;

import static org.codelibs.core.TestUtil.sameClass;
import static org.hamcrest.CoreMatchers.is;
import static org.hamcrest.CoreMatchers.nullValue;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertThat;

import java.lang.reflect.Field;
import java.util.Collection;
import java.util.Map;

      boolean permitsDuplicates,
      @Nullable String nullKey,
      @Nullable Integer nullValue) {
    multimap.clear();
    multimap.put("foo", 1);
    multimap.put("foo", 2);
    multimap.put("foo", 3);
    multimap.put("bar", 5);
    multimap.put("bar", -1);
    multimap.put(nullKey, nullValue);
    multimap.put("foo", nullValue);
    multimap.put(nullKey, 5);
    multimap.put("foo", 2);

```

### Type Conversion
```java
import org.codelibs.core.convert.*;

// Safe type conversions with null handling
Integer value = IntegerConversionUtil.toInteger("123");        // Returns 123
Integer nullValue = IntegerConversionUtil.toInteger(null);     // Returns null
Boolean flag = BooleanConversionUtil.toBoolean("true");        // Returns true
Date date = DateConversionUtil.toDate("2023-12-25", "yyyy-MM-dd");

    // null key
    InternalEntry<Object, Object, ?> nullEntry = segment.newEntryForTesting(null, hash, entry);
    Object nullValue = new Object();
    WeakValueReference<Object, Object, ?> nullValueRef =
        segment.newWeakValueReferenceForTesting(nullEntry, nullValue);
    segment.setWeakValueReferenceForTesting(nullEntry, nullValueRef);
    segment.setTableEntryForTesting(index, nullEntry);
    // skip the null key

    // null key
    InternalEntry<Object, Object, ?> nullEntry = segment.newEntryForTesting(null, hash, entry);
    Object nullValue = new Object();
    WeakValueReference<Object, Object, ?> nullValueRef =
        segment.newWeakValueReferenceForTesting(nullEntry, nullValue);
    segment.setWeakValueReferenceForTesting(nullEntry, nullValueRef);
    segment.setTableEntryForTesting(index, nullEntry);
    // skip the null key

        () -> ImmutableMap.ofEntries((Entry<Integer, Integer>) nullKey));
    Entry<@Nullable Integer, @Nullable Integer> nullValue = entry(23, null);
    assertThrows(
        NullPointerException.class,
        () -> ImmutableMap.ofEntries((Entry<Integer, Integer>) nullValue));
  }

  private static <T> Map<T, T> map(T... keysAndValues) {
    assertThat(keysAndValues.length % 2).isEqualTo(0);

    // null key
    DummyEntry<Object, Object> nullEntry = DummyEntry.create(null, hash, entry);
    Object nullValue = new Object();
    ValueReference<Object, Object> nullValueRef = map.newValueReference(nullEntry, nullValue, 1);
    nullEntry.setValueReference(nullValueRef);
    table.set(index, nullEntry);
    // skip the null key

    // null key
    DummyEntry<Object, Object> nullEntry = DummyEntry.create(null, hash, entry);
    Object nullValue = new Object();
    ValueReference<Object, Object> nullValueRef = map.newValueReference(nullEntry, nullValue, 1);
    nullEntry.setValueReference(nullValueRef);
    table.set(index, nullEntry);
    // skip the null key

    boolean nullKeys = inverseFeatures.remove(MapFeature.ALLOWS_NULL_KEYS);
    boolean nullValues = inverseFeatures.remove(MapFeature.ALLOWS_NULL_VALUES);

    if (nullKeys) {
      inverseFeatures.add(MapFeature.ALLOWS_NULL_VALUES);
    }
    if (nullValues) {
      inverseFeatures.add(MapFeature.ALLOWS_NULL_KEYS);
    }

    inverseFeatures.add(NoRecurse.INVERSE);