JavaのGsonライブラリを使用してJSON文字列をファイルに書き込む方法は？

import java.io.*;
import com.google.gson.*;
public class JSONToFileTest {
   public static void main(String[] args) throws IOException {
      Gson gson = new Gson();
      FileWriter fileWriter = new FileWriter("Student.json");
      Student student = new Student("Raja", "Ramesh", 30, "Hyderabad");
      gson.toJson(student, fileWriter);
      fileWriter.close();
      System.out.println("JSON string write to a file successfully");
      System.out.println(student);
   }
}
// Student class
class Student {
   private String firstName;
   private String lastName;
   private int age;
   private String address;
   public Student(String firstName, String lastName, int age, String address) {
      super();
      this.firstName = firstName;
      this.lastName = lastName;
      this.age = age;
      this.address = address;
   }
   public String getFirstName() {
      return firstName;
   }
   public void setFirstName(String firstName) {
      this.firstName = firstName;
   }
   public String getLastName() {
      return lastName;
   }
   public void setLastName(String lastName) {
      this.lastName = lastName;
   }
  public int getAge() {
     return age;
   }
   public void setAge(int age) {
      this.age = age;
   }
   public String getAddress() {
      return address;
   }
   public void setAddress(String address) {
      this.address = address;
   }
   public String toString() {
      return "Student[ " +
               "firstName = " + firstName +
               ", lastName = " + lastName +
               ", age = " + age +
               ", address = " + address +
             " ]";
   }
}

JSON string write to a file successfully
Student[ firstName = Raja, lastName = Ramesh, age = 30, address = Hyderabad ]