public class TestMyPoint {
  public static void main(String[] args) {

    // Step 1: 定義對象start和end
    MyPoint start = new MyPoint();
    MyPoint end = new MyPoint();

    // Step 2: 給 start and end的屬性賦值
    start.x = 10;
    start.y = 10;
    end.x = 20;
    end.y = 30;

    // Step 3: 輸出start 和 end
    System.out.println("Start point is " + start.toString());
    System.out.println("End point is " + end.toString());
    System.out.println();

    // Step 5: 定義對象stray并賦值為對象 end，此時stray與end引用同一對象
    MyPoint stray = end;

    // Step 6: 輸出stray和end
    System.out.println("Stray point is " + stray.toString());
    System.out.println("End point is " + end.toString());
    System.out.println();

    // Step 7: 給stray重新賦值
    stray.x = 47;
    stray.y = 50;
    System.out.println("Stray point is " + stray.toString());
    System.out.println("End point is " + end.toString());//stray的改變也影響end，因為end和stray引用同一對象
    System.out.println("Start point is " + start.toString());
  }
}