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It seems that when an object is allocated in a function, and never escapes that, Java would replace the allocation to stack if the reference is not modified, which means Java would not reuse previously allocated memory for new objects in this case.

e.g.

void stack() {
  Point2D.Double a = new Point2D.Double(0, 0);
  a.setLocation(1, 1);
}

a could be allocated on stack, while

void heap() {
  Point2D.Double b = new Point2D.Double(0, 0);
  b = new Point2D.Double(1, 1);
}

b can not be allocated on stack.

Meanwhile, builder functions behaves the same as constructors. e.g.

Point2D.Double origin() {
  return new Point2D.Double(0, 0);
}

void stack() {
  Point2D.Double a = origin();
  a.setLocation(1, 1);
}

behaves the same as previous example.