Java - Reading JSON from a JSON FILE and printing out each element?

The first thing, the JSON you show us is incorrect. Valid one would be:

[
  {
    "id": 8484,
    "name": "David",
    "height": "6",
    "weight": 165
  }
]

Last comma must be removed.

How to use Gson? It's easy. You need a class which will represent JSON as POJO (Plain Old Java Object). POJO is like skeleton. For you case I would write something like this:

public class Person {
    public int id;
    public String name;
    public int height;
    public int weight;
}

And then use Gson like this:

Gson gson = new Gson();
String json = "[{\"id\": 8484, \"name\": \"David\", \"height\": \"6\", \"weight\": 165}]";
//Because your JSON has array structure we need to give Gson array of our class
Person[] person = gson.fromJson(json, Person[].class);
//It will print: David 8484
System.out.println(person[0].name + " " + String.valueOf(person[0].id));

We don't need to give JSON as String, but fe. as reader of JSON file (FileReader).

If that didn't help, you propably don't have Gson in your project, but that is another question. Here is user guide for Gson: Gson User guide