sum of BigDecimal List using streams and sum method

问题:

If we have all int or long or other primitive datatype value in list then we obtain sun of all values using

return items.stream().mapToInt(i -> i).sum(); 

I have list of BigDecimal values,how to find the sum of all values using Java8

As there is no default method like mapToBigDecimal I tried to create plain map but then I cannot use sum()

回答1:

You can use Stream#reduce(BinaryOperator).

A simple example:

List<BigDecimal> items = Arrays.asList(BigDecimal.ONE, BigDecimal.valueOf(1.5), BigDecimal.valueOf(100)); items.stream().reduce((i, j) -> i.add(j)).ifPresent(System.out::println); // Outputs 102.5 

回答2:

List<BigDecimal> items = Arrays.asList(BigDecimal.ONE, BigDecimal.valueOf(1.5), BigDecimal.valueOf(100)); items.stream().reduce(BigDecimal.ZERO, BigDecimal::add); 

Though Answer provided by Lisq199 works but I am in favor of including Holger and Klitos comments,This handles No values and always returns a value

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