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Optional<Integer> optional1 = Optional.of(1);
Optional<Integer> optional2 = Optional.ofNullable(null);
Optional<Integer> optional3 = Optional.ofNullable(2);
optional3.get();
Optional<Integer> optional1 = Optional.ofNullable(null); Optional<Integer> optional2 = Optional.ofNullable(null); System.out.println(optional1 == optional2); System.out.println(optional1 == Optional.<Integer>empty()); Object o1 = Optional.<Integer>empty(); Object o2 = Optional.<String>empty(); System.out.println(o1 == o2);
Optional<Integer> optional1 = Optional.ofNullable(1);
optional1.ifPresent((t) -> { System.out.println("value is " + t); });
Optional<Integer> optional2 = Optional.ofNullable(null);
System.out.println(optional2.orElse(1000) == 1000);
System.out.println(optional1.orElseGet(() -> { return 1000; }) == 1);
optional1.orElseThrow(()->{throw new IllegalStateException();});
Optional<Integer> optional1 = Optional.ofNullable(1); Optional<Integer> filter1 = optional1.filter((a) -> a == null); System.out.println(filter1.isPresent());
Optional<Integer> optional1 = Optional.ofNullable(1); Optional<String> str1Optional = optional1.map((a) -> "key" + a); System.out.println(str1Optional.get()); System.out.println(str2Optional.isPresent());
Optional<Integer> optional1 = Optional.ofNullable(1); Optional<Optional<String>> str1Optional = optional1.map((a) -> { return Optional.<String>of("key" + a); }); Optional<String> str2Optional = optional1.flatMap((a) -> { return Optional.<String>of("key" + a); });
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