Save custom array of objects to file and read again in java?

Question

I would like to save an array of objects that is custom as a file and re-read it back as an array of objects on program start in java. If I could also save it as JSON, it would be nice. I have tried some common methods but I get a error saying that my array is not serialiazable.

class ArrayOfObjects {

  public static void main (String[] args) throws Exception {

    Students[] studentArray = new Students[3];
    studentArray[0] = new Students();
    studentArray[0].age = 18;
    studentArray[0].name = "Jones";
    studentArray[1] = new Students();
    studentArray[1].age = 21;
    studentArray[1].name = "David";
    studentArray[2] = new Students();
    studentArray[2].age = 15;
    studentArray[2].name = "Jeremy";
  }  

}

class Students {

  int age;
  String name;

}

user2717954 · Accepted Answer · 2014-10-19 11:58:41Z

1

your class Students should implement Serialiazble

answered Oct 19, 2014 at 11:58

user2717954

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2 Comments

jeremys Over a year ago

That sort of worked. I got this now. pastebin.com/6fwMEptN Also, how do I re-read it into the same array?

user2717954 Over a year ago

you use ObjectInputStream

mavarazy · Accepted Answer · 2014-10-19 12:04:08Z

0

If you want to save it in standard output, Students must implement Serializable.

If you wan to save it as JSON, use Jackson (http://fasterxml.com/) and normalise it Java bean declaration to the class.

class Students implemenst Serializable {

  private int age;
  private String name;

  public int getAge() {
      return age;
  }

  public void setAge(int age) {
      this.age = age;
  }

  public String getName() {
      return name;
  }

  public void setName(String name) {
      this.name = name;
  }

}

answered Oct 19, 2014 at 12:04

mavarazy

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