证明存在toString() ~~~ package obj.a5; public class Test { public static void main(String[] args){ String name =new String("你好"); System.out.println(name.toString()); } } ~~~ 自定义的类没有重写toString()时，输出toString()会输出内存地址 ~~~ package obj.a5; public class Test { public static void main(String[] args){ //String name =new String("你好"); Cat one=new Cat(); System.out.println(one); } } class Cat{ } ~~~  重写toString() ~~~ package obj.a5; public class Test { public static void main(String[] args){ //String name =new String("你好"); Cat one=new Cat(); System.out.println(one); } } class Cat{ String name; int age; public String toString(){ return "我的姓名是："+name+"我的年龄是："+age; } } ~~~