类 main 的方法未定义

Question

我正在编写一个简单的社交媒体模型，其中用户的朋友表示为一组Friend对象。

使用toStringFriendsmain 方法中使用的方法时，我收到了标题错误。有谁知道如何解决这个问题？

public class Friend {

private String name;

private String password;

private int uid;

private Friend [] friends;

public Friend (String name, String password, int uid, Friend [] friends) {

    this.name = name;

    this.password = password;

    this.uid = uid;

    this.friends [0] = friends [0];

}

public Friend [] getFriends () {

    return friends;

}

public String toStringFriends (Friend [] friends) {     

    String s = "";  

    for (int i = 0; i <= friends.length; i++) {

         s = s + (friends [i]).getName();

    }

    return s;

}

}

public class Main {

public static void main(String[] args) {

    Friend [] noFriends = new Friend [0];

    Friend [] laurasFriends = new Friend [1];           

    Friend jack = new Friend ("jack","liverpool",1,noFriends);  

    laurasFriends [0] = jack;

    Friend laura = new Friend ("laura","everton",2,laurasFriends);

    String s = toStringFriends(laurasFriends);

    System.out.println(s);  

    System.out.println(toStringFriends(laura.getFriends()));

}

}

Answer 1

要么toStringFriends()静态要么实例化一个 Friend 对象并在其上调用该方法。

Answer 2

您不能在没有对象的情况下调用实例或非静态方法。您应该使用一些实例对象，然后您可以通过.运算符调用。喜欢object.method()

Answer 3

您需要从laura对象的实例中调用它：String&nbsp;s&nbsp;=&nbsp;laura.toStringFriends(laurasFriends);