public @NotNull FileAssert isDirectory() {
    isNotNull();
    if (actual.isDirectory()) {
      return this;
    }
    failIfCustomMessageIsSet();
    throw failure(format("file:<%s> should be a directory", actual));
  }
public @NotNull FileAssert isDirectory() {
    isNotNull();
    if (actual.isDirectory()) {
      return this;
    }
    failIfCustomMessageIsSet();
    throw failure(format("file:<%s> should be a directory", actual));
  }
public @ NotNull FileAssert isDirectory ( ) { isNotNull ( ) ; if ( actual . isDirectory ( ) ) { return this ; } failIfCustomMessageIsSet ( ) ; throw failure ( format ( "file:<%s> should be a directory" , actual ) ) ; }
Verifies that the actual {@code File} is a directory.

@return this assertion object.
@throws AssertionError if the the actual {@code File} is {@code null}.
@throws AssertionError if the actual {@code File} is not a directory.
Verifies that the actual { @code File } is a directory .