Define the class inside the loop or only initialise it inside condition
if (s[0].equals("D")) {
Dreptunghi d = new Dreptunghi();
d.setX1(Double.parseDouble(s[1]));
d.setY1(Double.parseDouble(s[2]));
d.setX2(Double.parseDouble(s[3]));
d.setY2(Double.parseDouble(s[4]));
setDreptunghiuri.add(d);
}
or
if (s[0].equals("D")) {
d = new Dreptunghi();
d.setX1(Double.parseDouble(s[1]));
d.setY1(Double.parseDouble(s[2]));
d.setX2(Double.parseDouble(s[3]));
d.setY2(Double.parseDouble(s[4]));
setDreptunghiuri.add(d);
}