Question

如何将一种类型的给定Guava Range转换为另一种类型的范围。

我期待一种类似于Predicates.compose的compose方法。以Integer和Long为例：

Range<Integer> intRange = Range.compose(Range.atLeast(10l),integerFromLongFunction);

我写了撰写方法：

    public static <F extends Comparable<F>, T extends Comparable<T>> Range<T> compose(Range<F> range,
        Function<F, T> function) {
    Range<T> result;
    if (range.hasUpperBound() && range.hasLowerBound()) {
        T upperEndpoint = function.apply(range.upperEndpoint());
        T lowerEndpoint = function.apply(range.lowerEndpoint());
        result = Range.range(lowerEndpoint, range.lowerBoundType(), upperEndpoint, range.upperBoundType());
    } else if (range.hasUpperBound()) {
        result = Range.upTo(function.apply(range.upperEndpoint()), range.upperBoundType());
    } else if (range.hasLowerBound()) {
        result = Range.downTo(function.apply(range.lowerEndpoint()), range.lowerBoundType());
    } else {
        result = Range.all();
    }
    return result;
}

单元测试：

@Test
public void testLongRangeToInteger() {
    Integer inRange = 6;
    Integer outOfRange = 3;
    Range<Long> longRange = Range.atLeast(5l);
    assertTrue(longRange.apply(inRange.longValue()));
    assertFalse(longRange.apply(outOfRange.longValue()));

    Function<Long, Integer> function = integerFromLongFunction();
    Range<Integer> intRange = RangeExtended.compose(longRange, function);
    assertTrue(intRange.apply(inRange));
    assertFalse(intRange.apply(outOfRange));
}

public static Function<Long, Integer> integerFromLongFunction() {
    return new Function<Long, Integer>() {

        @Override
        public Integer apply(Long input) {
            return (input == null) ? null : input.intValue();
        }
    };
}

我目前的愿望实际上是将Joda持续时间转换为相应的毫秒，但为了简单起见，我在Long / Integer中编写了示例。

似乎番石榴会有这个，但我找不到任何地方。我使用v14，但是查看最新的v17 javadoc并没有暴露任何内容。

Answer 1

我认为这就是你要找的东西

public static final Function<Range<Duration>, Range<Long>> DURATION_RANGE_TO_LONG_RANGE = new Function<Range<Duration>, Range<Long>>() {

    @Override
    public Range<Long> apply(final Range<Duration> input) {

        return Range.range(input.lowerEndpoint()
                .getMillis(), input.lowerBoundType(), input.upperEndpoint()
                .getMillis(), input.upperBoundType());
    }

};

public static final void main(final String... args) {
    final List<Range<Duration>> durationRanges = ImmutableList.of(
            Range.closedOpen(Duration.millis(100), Duration.millis(200)),
            Range.closedOpen(Duration.millis(200), Duration.millis(300)));

    final List<Range<Long>> longRanges = FluentIterable.from(durationRanges)
        .transform(DURATION_RANGE_TO_LONG_RANGE)
        .toList();

    //[[100‥200), [200‥300)]
    System.out.println(longRanges);
}

将番石榴范围转换为不同类型

1 个答案: