Java：在“链接”列表中挑选多个元素

Question

I have a linked list of classes which contain 3 strings and a double. I want to collect the total value of each double in the list. For example

 LinkedList<Person> L = new LinkedList<Person>();
 Person p1 = new Person("Fee","Foo","Bar", 1.2);
 Person p2 = new Person("Fi","Fi","Fo", 2.5);
 L.add(p1);
 L.add(p2);

I would want to find and add up 1.2, and 2.5. I'm assuming I should use ListIterator, but how do I tell it to add each found double value to the total?

Answer 1

Just use a for loop over the persons:

double sum = 0;
for(Person p : L)
    sum += p.getDouble();
System.out.print(sum);

Answer 2

You have couple of options to iterate over it

A) Using iterators as asked

Person person = new Person();
ListIterator<Person> listIterator = L.listIterator();

while (listIterator.hasNext()) {
      person = listIterator.next();
      double value = person.getDoubleAttribute();
}

B) Use a for-each loop as suggested in other answer:

for(Person person : L){
    double value = person.getDoubleAttribute();
}

PS: is highly discouraged to start Java variables or attributes by UPPERCASE

Answer 3

You can iterate over the list, get the double property of each Person and sum them, or you can use Java 8 Streams :

double sum = L.stream().mapToDouble(Person::getDoubleProperty).sum();

Where getDoubleProperty stands for the name of a method in the Person class returning the double value.