Stream流 - 取最大对象、最小对象
public class Test3 {
public static void main(String[] args) throws ClassNotFoundException {
ArrayList<Dnl> dnls = new ArrayList<>();
dnls.add(new Dnl("11.1","22.2"));
dnls.add(new Dnl("22.1","66.2"));
dnls.add(new Dnl("33.1","44.2"));
dnls.add(new Dnl(null,"55.2"));
dnls.add(new Dnl("33.1",null));
//计算总和
BigDecimal sumYgz = dnls.stream().map(vo -> new BigDecimal(vo.getYgz() == null ? "0" : vo.getYgz())).reduce(BigDecimal.ZERO, BigDecimal::add);
BigDecimal sumWgz = dnls.stream().map(vo -> new BigDecimal(vo.getWgz() == null ? "0" : vo.getWgz())).reduce(BigDecimal.ZERO, BigDecimal::add);
System.out.println("sumYgz=" + sumYgz + ",sumWgz=" + sumWgz);
//最大值
//Optional<T> max(Comparator<? super T> comparator);
Optional<Dnl> max = dnls.stream().filter(vo -> vo.getYgz()!= null).max(new Comparator<Dnl>() {
@Override
public int compare(Dnl o1, Dnl o2) {
BigDecimal b1 = new BigDecimal(o1.getYgz());
BigDecimal b2 = new BigDecimal(o2.getYgz());
BigDecimal subtract = b1.subtract(b2);
return subtract.compareTo(BigDecimal.ZERO);
}
});
Dnl dnlmax = max.get();
System.out.println("最大有功总：" + dnlmax);
//lamda表达式简写
Optional<Dnl> max1 = dnls.stream().filter(vo -> vo.getWgz() != null).max((o1, o2) -> new BigDecimal(o1.getWgz()).subtract(new BigDecimal(o2.getWgz())).compareTo(BigDecimal.ZERO));
Dnl dnlmax1 = max1.get();
System.out.println("最大无功总：" + dnlmax1);
//最小值
//Optional<T> min(Comparator<? super T> comparator);
Optional<Dnl> min = dnls.stream().filter(vo -> vo.getYgz()!= null).min(new Comparator<Dnl>() {
@Override
public int compare(Dnl o1, Dnl o2) {
BigDecimal b1 = new BigDecimal(o1.getYgz());
BigDecimal b2 = new BigDecimal(o2.getYgz());
BigDecimal subtract = b1.subtract(b2);
return subtract.compareTo(BigDecimal.ZERO);
}
});
Dnl dnlmin = min.get();
System.out.println("最小有功总：" + dnlmin);
//lamda表达式简写
Optional<Dnl> min1 = dnls.stream().filter(vo -> vo.getWgz() != null).min((o1, o2) -> new BigDecimal(o1.getWgz()).subtract(new BigDecimal(o2.getWgz())).compareTo(BigDecimal.ZERO));
Dnl dnlmin1 = min1.get();
System.out.println("最小无功总：" + dnlmin1);
}
}