*/
  @Synchronized
  @Throws(IOException::class)
  operator fun get(key: String): Snapshot? {
    initialize()

    checkNotClosed()
    validateKey(key)
    val entry = lruEntries[key] ?: return null
    val snapshot = entry.snapshot() ?: return null

    redundantOpCount++
    journalWriter!!
      .writeUtf8(READ)
      .writeByte(' '.code)

    filesystem.setFaultyDelete(cacheDir, false)
    val snapshot = cache["k1"]
    assertThat(snapshot).isNull()
  }

  @ParameterizedTest
  @ArgumentsSource(FileSystemParamProvider::class)
  fun validateKey(parameters: Pair<FileSystem, Boolean>) {
    setUp(parameters.first, parameters.second)
    var key = ""
    assertFailsWith<IllegalArgumentException> {
      key = "has_space "
      cache.edit(key)

/**
 * Validation constraint to ensure that a string is a valid cron expression.
 */
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
@Documented
@Constraint(validatedBy = CronExpressionValidator.class)
public @interface CronExpression {

    /**
     * The error message when validation fails.
     * @return the error message
     */

        jakarta.validation.Constraint constraint = CronExpression.class.getAnnotation(jakarta.validation.Constraint.class);
        assertNotNull(constraint);
        Class<?>[] validators = constraint.validatedBy();
        assertEquals(1, validators.length);
        assertEquals(CronExpressionValidator.class, validators[0]);
    }

    // Test validation with valid cron expressions
    public void test_validCronExpressions() {

 * This annotation validates URI strings based on specified protocol types.
 */
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
@Documented
@Constraint(validatedBy = UriTypeValidator.class)
public @interface UriType {

    /**
     * Specifies the protocol type to validate against.
     *
     * @return the protocol type
     */
    ProtocolType protocolType();

/**
 * Validation constraint for custom size limits based on configuration keys.
 */
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
@Documented
@Constraint(validatedBy = CustomSizeValidator.class)
public @interface CustomSize {

    /**
     * The error message when validation fails.
     * @return the error message
     */

        assertNotNull("Constraint annotation should be present", constraint);
        assertEquals("Validator class should be UriTypeValidator", UriTypeValidator.class, constraint.validatedBy()[0]);
        assertEquals("Should have exactly one validator", 1, constraint.validatedBy().length);
    }

    // Test default values
    public void test_defaultValues() throws Exception {

        assertNotNull("Constraint annotation should be present", constraint);
        assertEquals("Validator class should be CustomSizeValidator", CustomSizeValidator.class, constraint.validatedBy()[0]);
    }

    // Test default values
    public void test_defaultValues() throws Exception {
        final Field field = CustomSizeTest.class.getDeclaredField("testField");