看看这段程序为什么有错呢

class person
{
 int age;
 void shout()
 {
  //int age=60;
  System.out.println("my age is"+age);
 }
  public static void main (String [] args)
  {
   person p1 = new person();
   person p2 = new person();
   p1.age = -30;
   p1.shout();
   p2.shout();
   String str1 = new String ("abc");
   String str2 = new String ("abc");
   String srt3 = str1;
   if(str1 == str3)
     System.out.println("ture");
    else
       System.out.println("false");
  }
}

  这段程序看了半天找不出毛病，但是总是提示第19行又错了，谁能告诉我哪里错了