reduce--遍历元素计算 具体的计算公式需要传入 结合BigDecimal

reduce--遍历元素计算 具体的计算公式需要传入 结合BigDecimal
        
        @Test
    public void testReduce() {
        Stream<Integer> stream = Arrays.stream(new Integer[]{1, 2, 3, 4, 5, 6, 7, 8});
         Stream<BigDecimal> stream1 = Arrays.stream(new BigDecimal[]{1, 2, 3, 4, 5, 6, 7, 8});
        没有返回0
       BigDecimal sum = stream1.stream().reduce(BigDecimal::add).orElse(BigDecimal.ZERO);
       
        //求集合元素只和  初始值为0
        Integer result = stream.reduce(0, Integer::sum);
        System.out.println(result);

        stream = Arrays.stream(new Integer[]{1, 2, 3, 4, 5, 6, 7});

        //求和
        stream.reduce((i, j) -> i + j).ifPresent(System.out::println);

        stream = Arrays.stream(new Integer[]{1, 2, 3, 4, 5, 6, 7});
        //求最大值
        stream.reduce(Integer::max).ifPresent(System.out::println);

        stream = Arrays.stream(new Integer[]{1, 2, 3, 4, 5, 6, 7});
        //求最小值
        stream.reduce(Integer::min).ifPresent(System.out::println);

        stream = Arrays.stream(new Integer[]{1, 2, 3, 4, 5, 6, 7});
        //做逻辑
        stream.reduce((i, j) -> i > j ? j : i).ifPresent(System.out::println);

        stream = Arrays.stream(new Integer[]{1, 2, 3, 4, 5, 6, 7});

        //求逻辑求乘机
        int result2 = stream.filter(i -> i % 2 == 0).reduce(1, (i, j) -> i * j);

        Optional.of(result2).ifPresent(System.out::println);
    }