java中各种类型用Stream流求最大值最小值

java中各种类型用Stream流求最大值最小值

一、BigDecimal 求最大值和最小值

1. 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);

2. 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);

二、Integer 求最大值和最小值

1. 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. 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();

3. 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);

三、Long 求最大值和最小值

1. 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);

2. 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. 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);

四、Double 求最大值和最小值

1. 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);

2. Collectors.summarizingLong()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();

3. 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);