How to find minimum of BigDecimal field in collection with java streams?

问题

I want to use java streams to iterate a list and find the BigDecimal minimum price. The following illustrates, but does not work (because min() cannot accept BigDecimal.

class Product {
    public BigDecimal price;
}

List<Product> products;
products.stream().min((Product) p -> p.price);

回答1:

Since BigDecimal already is Comparable, it is as simple as :

 BigDecimal min = products
        .stream()
        .map(Product::getPrice)
        .min(Comparator.naturalOrder())
        .orElse(BigDecimal.ZERO);

回答2:

You don't need a stream to find the minimum. Use Collections.min:

Collections.min(products, Comparator.comparing(p -> p.price));

回答3:

Did you try :

Product minProductPrice = producs.stream()
        .min((o1, o2) -> o1.price.compareTo(o2.price)).get();

回答4:

To solve this, please use the following code:

products.stream().min(Comparator.comparing(p -> p.price)).get();

Comparator.comparing method requires a Function that takes an input and returns a Comparable. This Comparable, in turn, is used by the comparing method to create a Comparator. The min method uses the Comparator to compare the elements in the stream. The lambda expression p->p.price creates a Function that takes an BigDecimal and returns an BigDecimal (which is a Comparable). Here, the lambda expression does not do much but in situations where you have a class that doesn't implement Comparable and you want to compare objects of that class using a property of that class that is Comparable, this is very useful. The call to get() is required because max(Comparator) return an Optional object.

回答5:

You can use the below as well,

BigDecimal bigDecimal = products.stream()
            .map(d -> d.getPrice())
            .reduce(BigDecimal::min).get();

System.out.println(bigDecimal.longValueExact());

来源：https://stackoverflow.com/questions/47712344/how-to-find-minimum-of-bigdecimal-field-in-collection-with-java-streams

标签

java

java-8

java-stream