if (o instanceof String s) { System.out.println(s.length()); } Object o = "test"; if (o instanceof String) { String s = (String) o; System.out.println(s.length()); }
getName(Shape s) { if (s instanceof Circle) { return "円"; } else if (s instanceof Rectangle) { return "四角"; } else if (s instanceof Square) { return "正方形"; } }
Bar Baz sealed 要 sealed 要 final or non-sealed 要 final or non-sealed MyBaz Bazがnon-sealedであれば 継承できる。sealされない sealed class Hoge permits Foo, Bar {} final class Foo extends Hoge {} sealed class Bar extends Hoge permits Baz {} non-sealed class Baz extends Bar {} class MyBaz extends Baz {}