How to generate same object with different values into an ArrayList?

Question

I have an ArrayList and I want to save some planets from the solar system as shapes into this ArrayList, but at the end, only the last object parameter is saved as many objects are there in all.

This is in main:

ArrayList<Shape> shapes = new ArrayList<Shape>();
void setup() {
  size(1600, 800);
  generateSolarSystem();
}
void draw() {
  update();
  //background(255);
  int begin_x = 100;
  int begin_y = 100;
  int distance = 1;

  for (Shape s : shapes) {
   pushMatrix();
     translate(begin_x+distance, begin_y);
     scale(1.1, 1.1);
     s.Draw(); 

     text(s.name, begin_x+distance, begin_y+10);
     distance += 100;
     System.out.println("name: " + s.name); /*3*/
    popMatrix();
  } 
}
void generateSolarSystem() {
  /**/
  int d = 10;
  /**/
  Shape planet = new Circle();;
  for(int idx = 0; idx<9; ++idx){
    switch(idx) {
      case 0: 
        //Mercury
        planet.planet_color_r = 128;
        planet.planet_color_g = 128;
        planet.planet_color_b = 128;
        planet.name = "Mercury";
        planet.mass = "33011 x 10^23";
        break;
      case 1: 
        // Venus
        planet.planet_color_r = 255;
        planet.planet_color_g = 255;
        planet.planet_color_b = 0;
        planet.name = "Venus";
        planet.mass = "4.8675 × 10^24 kg";
        break;
      case 2: 
        // Earth
        planet.planet_color_r = 0;
        planet.planet_color_g = 0;
        planet.planet_color_b = 255;
        planet.name = "Earth";
        planet.mass = "4.8675 × 10^24 kg";
        break;
      case 3: 
        // Mars
        planet.planet_color_r = 255;
        planet.planet_color_g = 128;
        planet.planet_color_b = 0;
        planet.name = "Mars";
        planet.mass = "4.8675 × 10^24 kg";
        break;
      case 4: 
        // Jupiter
        planet.planet_color_r = 150;
        planet.planet_color_g = 75;
        planet.planet_color_b = 0;
        planet.name = "Jupiter";
        planet.mass = "4.8675 × 10^24 kg";
        break;
      case 5: 
        // Saturn
        planet.planet_color_r = 147;
        planet.planet_color_g = 131;
        planet.planet_color_b = 105;
        planet.name = "Saturn";
        planet.mass = "4.8675 × 10^24 kg";
        break;
      case 6: 
        // Uranus
        planet.planet_color_r = 140;
        planet.planet_color_g = 205;
        planet.planet_color_b = 216;
        planet.name = "Uranus";
        planet.mass = "4.8675 × 10^24 kg";
        break;
      case 7: 
        // Neptune
        planet.planet_color_r = 53;
        planet.planet_color_g = 110;
        planet.planet_color_b = 163;
        planet.name = "Neptune";
        planet.mass = "4.8675 × 10^24 kg";
        break;
      case 8: 
        // Pluto
        planet.planet_color_r = 194;
        planet.planet_color_g = 196;
        planet.planet_color_b = 168;
        planet.name = "Pluto";
        planet.mass = "4.8675 × 10^24 kg";
        break;
    }

    shapes.add(planet);
    /*1*/
    text("added: " + planet.name, 10, d);
    d += 10;
    /**/
  }

  //check
  d += 10;
  for(Shape s : shapes) {
    /*2*/
    text("check - " + s.name, 10, d);
    d += 10;
  }
}

And this is a Shape:

abstract class Shape {

  PVector position = new PVector();  
  PVector fill_color = new PVector(0, 0, 0);
  PVector stroke_color = new PVector(0, 0, 0);  
  PVector select_fill_color = new PVector(255, 0, 0);
  PVector select_stroke_color = new PVector(255, 0, 0);

  Boolean selected = false;

  int planet_color_r;
  int planet_color_g;
  int planet_color_b;
  String name;
  String mass;

  int detailness = 10;

  abstract void Draw();
  abstract Boolean Contains(int x, int y);
}

At /*1*/ the name of planets is seems good, but at /*2*/ and at /*3*/ every planet name is "Pluto". Why? How can I resolve this?

Try moving Shape planet = new Circle();; inside for loop, removing double ; , and instead ++idx try with idx++ — bakero98
– bakero98, Commented Sep 30, 2018 at 21:29

Mureinik · Accepted Answer · 2018-09-30 21:32:36Z

1

You keep overriding the same planet object. Instead, you should create a new object for each iteration in the loop:

for (int idx = 0; idx < 9; ++idx) {
    Shape planet = new Circle(); // Inside the loop!
    switch(idx) {

answered Sep 30, 2018 at 21:32

Mureinik

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Comments

Kevin Workman · Accepted Answer · 2018-09-30 21:29:43Z

0

Right now, you're only ever creating a single instance of Circle.

You're then looping over your planet indexes and setting the fields in that index to different values. This is why only your last iteration of the loop looks like it's saved.

To fix your problem, you need to create a new instance of Circle each iteration of the loop. In other words, switch the order of these two lines:

Shape planet = new Circle();
for(int idx = 0; idx<9; ++idx){

answered Sep 30, 2018 at 21:29

Kevin Workman

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