How To Solve Stream Sum Precision Problem

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How To Solve Stream Sum Precision Problem

這篇介紹How To Solve Stream Sum Precision Problem。

有精確度問題的example

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int sum = persons.stream()
		 .filter(person -> person.getGender() == Person.Gender.MALE)
		 .mapToDouble(Person::getWeight)
		 .sum();

當Weight欄位數值有無窮小數點時，做sum運算會有精確度問題。

使用reduce

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int sum = persons.stream()
		 .filter(person -> person.getGender() == Person.Gender.MALE)
		 .mapToDouble(Person::getWeight)
		 .reduce((total, weight) ->  BigDecimalUtils.add(total, weight).doubleValue())
		 .getAsDouble();