1 BigDecimal类型数值求最大最小值

1.1 for循环实现

        List<BigDecimal> list = new ArrayList<>(Arrays.asList(new BigDecimal(1), new BigDecimal(2)));
        BigDecimal max = list.get(0);
        BigDecimal min = list.get(0);
        for (BigDecimal decimal : list) {
            if (max.compareTo(decimal) < 0) {
                max = decimal;
            }
            if (min.compareTo(decimal) > 0) {
                min = decimal;
            }
        }

1.2 stream().reduce()实现

        List<BigDecimal> list = new ArrayList<>(Arrays.asList(new BigDecimal(1), new BigDecimal(2)));
        BigDecimal max = list.stream().reduce(list.get(0), BigDecimal::max);
        BigDecimal min = list.stream().reduce(list.get(0), BigDecimal::min);

1.3 stream().max()或stream().min()实现 

        List<BigDecimal> list = new ArrayList<>(Arrays.asList(new BigDecimal(1), new BigDecimal(2)));
        BigDecimal max = list.stream().max(Comparator.comparing(x -> x)).orElse(null);
        BigDecimal min = list.stream().min(Comparator.comparing(x -> x)).orElse(null);

 1.4 Collectors.maxBy()或Collectors.minBy()实现 

        List<BigDecimal> list = new ArrayList<>(Arrays.asList(new BigDecimal(1), new BigDecimal(2)));
        BigDecimal max = list.stream().collect(Collectors.maxBy(Comparator.comparing(x -> x))).orElse(null);
        BigDecimal min = list.stream().collect(Collectors.minBy(Comparator.comparing(x -> x))).orElse(null);

2 Integer类型数值求最大最小值

​ 2.1 for循环实现

        List<Integer> list = new ArrayList<>(Arrays.asList(1, 2));
        Integer max = list.get(0);
        Integer min = list.get(0);
        for (Integer num : list) {
            if (num > max) {
                max = num;
            }
            if (num < min) {
                min = num;
            }
        }

2.2 stream().reduce()实现

        List<Integer> list = new ArrayList<>(Arrays.asList(1, 2));
        Integer max = list.stream().reduce(list.get(0), Integer::max);
        Integer min = list.stream().reduce(list.get(0), Integer::min);

2.3 Collectors.summarizingInt()实现

        List<Integer> list = new ArrayList<>(Arrays.asList(1, 2));
        IntSummaryStatistics intSummaryStatistics = list.stream().collect(Collectors.summarizingInt(x -> x));
        Integer max = intSummaryStatistics.getMax();
        Integer min = intSummaryStatistics.getMin();

2.4 stream().max()或stream().min()实现

        List<Integer> list = new ArrayList<>(Arrays.asList(1, 2));
        Integer max = list.stream().max(Comparator.comparing(x -> x)).orElse(null);
        Integer min = list.stream().min(Comparator.comparing(x -> x)).orElse(null);

2.5 Collectors.maxBy()或Collectors.minBy()实现

        List<Integer> list = new ArrayList<>(Arrays.asList(1, 2));
        Integer max = list.stream().collect(Collectors.maxBy(Comparator.comparing(x -> x))).orElse(null);
        Integer min = list.stream().collect(Collectors.minBy(Comparator.comparing(x -> x))).orElse(null);

3 Long类型数值求最大最小值

3.1 for循环实现

        List<Long> list = new ArrayList<>(Arrays.asList(1L, 2L));
        Long max = list.get(0);
        Long min = list.get(0);
        for (Long num : list) {
            if (num > max) {
                max = num;
            }
            if (num < min) {
                min = num;
            }
        }

3.2 stream().reduce()实现 

        List<Long> list = new ArrayList<>(Arrays.asList(1L, 2L));
        Long max = list.stream().reduce(list.get(0), Long::max);
        Long min = list.stream().reduce(list.get(0), Long::min);

3.3 Collectors.summarizingLong()实现

        List<Long> list = new ArrayList<>(Arrays.asList(1L, 2L));
        LongSummaryStatistics summaryStatistics = list.stream().collect(Collectors.summarizingLong(x -> x));
        Long max = summaryStatistics.getMax();
        Long min = summaryStatistics.getMin();

3.4 stream().max()或stream().min()实现

        List<Long> list = new ArrayList<>(Arrays.asList(1L, 2L));
        Long max = list.stream().max(Comparator.comparing(x -> x)).orElse(null);
        Long min = list.stream().min(Comparator.comparing(x -> x)).orElse(null);

3.5 Collectors.maxBy()或Collectors.minBy()实现

        List<Long> list = new ArrayList<>(Arrays.asList(1L, 2L));
        Long max = list.stream().collect(Collectors.maxBy(Comparator.comparing(x -> x))).orElse(null);
        Long min = list.stream().collect(Collectors.minBy(Comparator.comparing(x -> x))).orElse(null);

4 Double类型数值求最大最小值

4.1 for循环实现

        List<Double> list = new ArrayList<>(Arrays.asList(1d, 2d));
        Double max = list.get(0);
        Double min = list.get(0);
        for (Double num : list) {
            if (num > max) {
                max = num;
            }
            if (num < min) {
                min = num;
            }
        }

4.2 stream().reduce()实现 

        List<Double> list = new ArrayList<>(Arrays.asList(1d, 2d));
        Double max = list.stream().reduce(list.get(0), Double::max);
        Double min = list.stream().reduce(list.get(0), Double::min);

4.3 Collectors.summarizingDouble()实现

        List<Double> list = new ArrayList<>(Arrays.asList(1d, 2d));
        DoubleSummaryStatistics summaryStatistics = list.stream().collect(Collectors.summarizingDouble(x -> x));
        Double max = summaryStatistics.getMax();
        Double min = summaryStatistics.getMin();

4.4 stream().max()或stream().min()实现 

        List<Double> list = new ArrayList<>(Arrays.asList(1d, 2d));
        Double max = list.stream().max(Comparator.comparing(x -> x)).orElse(null);
        Double min = list.stream().min(Comparator.comparing(x -> x)).orElse(null);

4.5 Collectors.maxBy()或Collectors.minBy()实现

        List<Double> list = new ArrayList<>(Arrays.asList(1d, 2d));
        Double max = list.stream().collect(Collectors.maxBy(Comparator.comparing(x -> x))).orElse(null);
        Double min = list.stream().collect(Collectors.minBy(Comparator.comparing(x -> x))).orElse(null);