java

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cat类中加上无参构造方法啊、
public class Nine2 {
public static void main(String[] args) {
// fun(new cat("ds","f"));
animal an=new cat("猫","喵~喵！");
System.out.println(an.jiao());
}
public static void fun(animal a) {
a.jiao();
}
}abstract class animal {
String name;
String call;
public abstract String jiao();
}class cat extends animal {
public cat(String name, String call) {
this.name=name;
this.call=call;
}
public cat() {
}
public String jiao() {
return name+call;
}
}
类名最好用大写字母开头,Animal,Cat
加上五参构造函数
public cat() {     }一般的类都应该有无参构造方法
fun(new cat("黑猫","mi mi"));
package test;public class Nine2 {
public static void main(String[] args) {
/*
animal an=new cat("猫","喵喵！");
System.out.println(an.jiao());
animal ann=new cat("狗","汪汪！");
System.out.println(ann.jiao());
*/
fun(new cat("猫","mimi"));
}
public static void fun(animal a)
{
a.jiao();
}
}
abstract class animal
{
String name;
String call;
public abstract String jiao();
}
class cat extends animal
{
     public cat(String name,String call)
    {
        this.name=name;
        this.call=call;
    }
     public String jiao()
    {
     return "这个动物：“"+this.name+"”它的叫声是：“"+this.call+"”";
       //System.out.println(this.name+this.call);
     }}class dog extends animal
{
     public dog(String name,String call)
    {
        this.name=name;
        this.call=call;
    }
     public String jiao()
    {
     return this.name+this.call;
       //System.out.println(this.name+this.call);
     }}请问我这样写为什么没有结果啊？
楼主你这个return写的不太对吧~ 同为学习中