```

### 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

        // setObject should handle various inputs
        try {
            WebApiUtil.setObject("validKey", "validValue");
            WebApiUtil.setObject("", "emptyKey");
            WebApiUtil.setObject("nullValue", null);
            WebApiUtil.setObject(null, "nullKey");
            WebApiUtil.setObject(null, null);
        } catch (Exception e) {

    // 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