运行下面程序后的输出结果是（）
public class Test {
  public static void main(String[] args) {
    StringBuffer a = new StringBuffer(“A”);
    StringBuffer b = new StringBuffer(“B”);
    operator(a, b);
    System.out.println(a + “,” + b);
  }
  public static void operator(StringBuffer x, StringBuffer y) {
    x.append(y); y = x;
  }
}