根据List中的对象的某个属性，求和

一、根据List中的对象的某个属性，求和

double mathAverageInt = list.stream().mapToInt( Student::getMathScoresInt ).average().orElse(0d);
double mathAverageLong = list.stream().mapToLong( Student::getMathScoresLong ).average().orElse(0d);
double mathAverageDouble = list.stream().mapToDouble( Student::getMathScoresDouble ).average().orElse(0d);
BigDecimal kczl = entities.stream().map(BloodRkdEntity::getKcxl).reduce(BigDecimal.ZERO, BigDecimal::add);

二、根据List中的对象的某个属性，求平均值

double mathAverageInt = list.stream().mapToInt( Student::getMathScoresInt ).average().orElse(0d);
double mathAverageLong = list.stream().mapToLong( Student::getMathScoresLong ).average().orElse(0d);
double mathAverageDouble = list.stream().mapToDouble( Student::getMathScoresDouble ).average().orElse(0d);

三、根据List中的对象的某个属性，求最大值

int mathMaxInt = list.stream().mapToInt( Student::getMathScoresInt ).max().getAsInt(); //int类型
long mathMaxLong = list.stream().mapToLong( Student::getMathScoresLong ).max().getAsLong();
double mathMaxDouble = list.stream().mapToDouble( Student::getMathScoresDouble ).max().getAsDouble();
BigDecimal mathMaxBigDecimal = list.stream().map( Student::getMathScoresBigDecimal ).reduce(BigDecimal.ZERO, BigDecimal::max);

四、根据List中的对象的某个属性，求最小值

int mathMinInt = list.stream().mapToInt( Student::getMathScoresInt ).min().getAsInt();
long mathMinLong = list.stream().mapToLong( Student::getMathScoresLong ).min().getAsLong();
double mathMinDouble = list.stream().mapToDouble( Student::getMathScoresDouble ).min().getAsDouble();
BigDecimal mathMinBigDecimal = list.stream().map( Student::getMathScoresBigDecimal ).reduce(BigDecimal.ZERO, BigDecimal::min);