Question

我有一个包含ff数据的2列列表：

-4123.800000000000;"type1"
-67.620000000000;"type2"
-3128.870000000000;"type2"
-2443.770000000000;"type1"
-30000.000000000000;"type1"
-812.580000000000;"type3"
-8062.990000000000;"type3"
-177.800000000000;"type1"
-28655.400000000000;"type2"

我尝试使用for循环，并在类型相同时添加金额。这可能是for循环还是有更好的方法。

for (int i = 0; i < vecRow.size(); i++) {
    // Do something
}

Answer 1

在java 8中：

    Stream.of("-4123.800000000000;\"type1\"",
            "-67.620000000000;\"type2\"",
            "-3128.870000000000;\"type2\"",
            "-2443.770000000000;\"type1\"",
            "-30000.000000000000;\"type1\"",
            "-812.580000000000;\"type3\"",
            "-8062.990000000000;\"type3\"",
            "-177.800000000000;\"type1\"",
            "-28655.400000000000;\"type2\"")
            .map((s) -> s.split(";", 2))
            .collect(Collectors.toMap(
                    (fields) -> fields[1].replace("\"", ""),
                    (fields) -> new BigDecimal(fields[0]),
                    (oldValue, newValue) -> newValue.add(oldValue)))
            .entrySet()
            .forEach((s) -> System.out.println(s));

或部分更好地理解

    String[] vecRow = {
            "-4123.800000000000;\"type1\"",
            "-67.620000000000;\"type2\"",
            "-3128.870000000000;\"type2\"",
            "-2443.770000000000;\"type1\"",
            "-30000.000000000000;\"type1\"",
            "-812.580000000000;\"type3\"",
            "-8062.990000000000;\"type3\"",
            "-177.800000000000;\"type1\"",
            "-28655.400000000000;\"type2\"",
    };
    Map<String, BigDecimal> map = Stream.of(vecRow)
        .map((s) -> s.split(";", 2))
        .peek((ss) -> System.out.println(Arrays.toString(ss)))
        .collect(Collectors.toMap(
                (fields) -> fields[1].replace("\"", ""),
                (fields) -> new BigDecimal(fields[0]),
                (oldValue, newValue) -> newValue.add(oldValue)));
    map.entrySet()
        .forEach((s) -> System.out.println(s));

因为明显需要精确的，所以不能使用double，因此：BigDecimal。

Collectors.mapTo这里有关键映射器，值映射器和 - 需要求和 - BigDecimal combiner(BigDecimal, BigDecimal)。

type3=-8875.570000000000
type2=-31851.890000000000
type1=-36745.370000000000

Java for循环：比较行和总和匹配

1 个答案: