单选题 阅读下段代码:class Dog { public String name; Dog(String name){ this.name =name; }}public class Demo1 { public static void main(String[] args){ Dog dog1 = new Dog("xiaohuang"); Dog dog2 = new Dog("xiaohuang"); String s1 = dog1.toString(); String s2 = dog2.toString(); String s3 = "xiaohuang"; String s4 = "xiaohuang"; }}返回值为true的是( )