Getting objects in linked lists vs. arrays in java

Use generics:

List<Person> people = new LinkedList<Person>();
// …
people.get(0).setName("steve");

You should use generics: List<Person>. Then you would be able to use people.get(0).setName(..)

Note that Java naming convention requires your variable to be lowercase.

You dont set which type of objects you store. So you need upcast:

Person person = (Person)People.get(0);
person.setName("steve");

or set type of stored objects:

List<Person> people = new LinkedList<Person>();

LinkedList is only good when you want to iterate quickly over the list, and when you want to quickly get to the first or last element. Also, you need to properly define people as a LinkedList to have access to the linked list methods, and you should type your list, so:

LinkedList<Person> people = new LinkedList<Person>();
people.getFirst().setName();

However, ArrayList is a better general choice, which offers good performance when accessing elements by their index, so:

List<Person> people = new ArrayList<Person>();

then

people.get(0).setName("fred");

If using Java 1.4 or earlier you need to cast it to People class:

((Person)People.get(0)).setName("SomeName");

If using Java 1.5 or later use generics:

List<Person> people = new LinkedList();

You need to define the Linked list as a Person LinkedList:

LinkedList<Person> people = new LinkedList<Person>();
people.get(0).setName("Steve");

Another note(not about the question, just to improve your Java): You use lowercase on the first letter of variable names, because of Java conventions and any subsequent word's first letter are capitalized;

float personsAge = 57.47;

EXPLANATION(Ignore if easily bored):

The LinkedList was not set to store a specific variable type. Another way to have solved this problem would have been:

LinkedList people = new LinkedList();
Person person = (Person) people.get(0);
person.setName("steve2")

Although you would have to do this to each 'Person' in the people list, defeating the point of the LinkedList.