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  1. import java.time.LocalDateTime;
  2. import java.math.BigInteger;
  3. import java.util.Arrays;
  4. import java.util.List;
  5. import java.util.function.Consumer;
  6. import java.util.function.Function;
  7. import java.util.stream.Stream;
  8.  
  9. class Untitled {
  10.     public static void main(String[] args) {
  11.         List<ExclusiveField> exclusiveFields = Arrays.asList(
  12.             ExclusiveField.withBigIntegerValue(BigInteger.ONE),
  13.             ExclusiveField.withDateValue(LocalDateTime.now()),
  14.             ExclusiveField.withStringValue("ABC")
  15.         );
  16.  
  17.         for(ExclusiveField field : exclusiveFields) {
  18.             field.consume(
  19.                 i -> System.out.println("Value was a BigInteger: " + i),
  20.                 d -> System.out.println("Value was a LocalDateTime: " + d),
  21.                 s -> System.out.println("Value was a String: " + s)
  22.             );
  23.         }
  24.     }
  25. }
  26. interface ExclusiveField {
  27.     static ExclusiveField withBigIntegerValue(BigInteger i) {
  28.         return (biM, dM, sM) -> biM.accept(i);
  29.     }
  30.     static ExclusiveField withDateValue(LocalDateTime d) {
  31.         return (biM, dM, sM) -> dM.accept(d);
  32.     }
  33.     static ExclusiveField withStringValue(String s) {
  34.         return (biM, dM, sM) -> sM.accept(s);
  35.     }
  36.  
  37.     void consume(
  38.         Consumer<BigInteger> bigIntegerMatcher, Consumer<LocalDateTime> dateMatcher, Consumer<String> stringMatcher);
  39.  
  40.     default <R> R map(
  41.         Function<BigInteger, R> bigIntegerMatcher, Function<LocalDateTime, R> dateMatcher, Function<String, R> stringMatcher) {
  42.  
  43.         Stream.Builder<R> b = Stream.builder();
  44.         consume(adapt(bigIntegerMatcher, b),adapt(dateMatcher, b),adapt(stringMatcher, b));
  45.         return b.build().findFirst().get();
  46.     }
  47.     static <T,R> Consumer<T> adapt(Function<T,R> f, Consumer<R> c) {
  48.         return t -> c.accept(f.apply(t));
  49.     }
  50. }
  51.  
Success #stdin #stdout 0.16s 2184192KB
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stdin
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Standard input is empty
stdout
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Value was a BigInteger: 1
Value was a LocalDateTime: 2019-05-09T07:05:17.348
Value was a String: ABC
https://ideone.com/gdw8ek
language:
Java (HotSpot 12)
created:
4 years ago
visibility:
public

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