javascript - Java 错误：找不到符号

Question

我已经在这个程序上工作了一段时间了，我一直在努力解决这个问题。我是编程新手，所以我不明白如何解决它。到目前为止，我已经设法消除了大部分错误，但这是我由于某种原因无法修复的错误。有人能帮我吗？我真的很感激。

import java.util.Scanner;
import java.util.ArrayList;
public class PetSorter
{
  public static void main (String [] args)
  {
    ArrayList<Pet> strList = new ArrayList<Pet>();
    Boolean another = true;
    Scanner keyboard = new Scanner(System.in);
    while(another)
    {
      System.out.println("Enter the pet's name: ");
      String nam = keyboard.nextLine();
      Pet p = new Pet(nam); //here is where the Error occurs
      strList.add(p);

      System.out.println("Would you like to enter another pet's name? (y/n)");
      String answer = keyboard.nextLine();
      another = answer.equalsIgnoreCase("y");
    }

    PetSorter.nameSort(strList);
    for (int x = 0; x < strList.size(); x++)
    {
      System.out.println(strList.get(x).getName());
    }
  }

  public static void nameSort (ArrayList<Pet> array)
  {
    for (int i = 1; i < array.size(); i++)
    {
      int j = i;
      Pet tp = array.get(i);
      String B = array.get(i).getName();
      while ((j > 0) && (array.get(j-1).getName().compareTo(B) > 0 ))
      {
        array.set(j, array.get(j-1));
        j--;
      }
      array.set(j,tp);
    }
  }
}

下面是宠物类

import java.util.ArrayList;
import java.util.Scanner;
public class Pet
{
    private String name;
    private int age; //in years
    private double weight; //in pounds

    /**
     This main is just a demonstration program.
    */
    public static void main(String[] args)
    {
        Pet myDog = new Pet( );
        myDog.set("Fido", 2, 5.5);
        myDog.writeOutput( );
        System.out.println("Changing name.");
        myDog.set("Rex");
        myDog.writeOutput( );
        System.out.println("Changing weight.");
        myDog.set(6.5);
        myDog.writeOutput( );
        System.out.println("Changing age.");
        myDog.set(3);
        myDog.writeOutput( );
    }

    public void writeOutput( )
    {
        System.out.println("Name: " + name);
        System.out.println("Age: " + age + " years");
        System.out.println("Weight: " + weight + " pounds");
    }

    public void set(String newName)
    {
        name = newName;
        //age and weight are unchanged.
    }

    public void set(int newAge)
    {
        if (newAge <= 0)
        {
            System.out.println("Error: illegal age.");
            System.exit(0);
        }
        else
            age = newAge;
        //name and weight are unchanged.
    }

    public void set(double newWeight)
    {
        if (newWeight <= 0)
        {
            System.out.println("Error: illegal weight.");
            System.exit(0);
        }
        else
            weight = newWeight;
        //name and age are unchanged.
    }

    public void set(String newName, int newAge, double newWeight)
    {
        name = newName;
        if ((newAge <= 0) || (newWeight <= 0))
        {
            System.out.println("Error: illegal age or weight.");
            System.exit(0);
        }
        else
        {
            age = newAge;
            weight = newWeight;
        }
    }

    public String getName( )
    {
        return name;
    }


    public int getAge( )
    {
        return age;
    }
    public double getWeight( )
    {
        return weight;
    }
}

Answer 1

Pet将所需的 constrcutor添加到您的班级：

public class Pet {

    String name;

    ...

    public Pet (String name) {
        this.name = name;
    } 

    ...

}

Answer 2

用。。。来代替

  Pet p = new PetSorter().new Pet(nam); //here is where the Error occurs

并添加类 Pet

新代码：

import java.util.Scanner;
import java.util.ArrayList;
public class PetSorter
{

public class Pet
{
    String name;

    public Pet(String _name)
    {
    name=_name; 
    }

    public String getName()
    {
    return name;
    }
}


  public static void main (String [] args)
  {
    ArrayList<Pet> strList = new ArrayList<Pet>();
    Boolean another = true;
    Scanner keyboard = new Scanner(System.in);
    while(another)
    {
  System.out.println("Enter the pet's name: ");
  String nam = keyboard.nextLine();

  Pet p = new PetSorter().new Pet(nam); //here is where the Error occurs
  strList.add(p);

  System.out.println("Would you like to enter another pet's name? (y/n)");
  String answer = keyboard.nextLine();
  another = answer.equalsIgnoreCase("y");
    }

    PetSorter.nameSort(strList);
    for (int x = 0; x < strList.size(); x++)
    {
  System.out.println(strList.get(x).getName());
    }
  }

  public static void nameSort (ArrayList<Pet> array)
  {
    for (int i = 1; i < array.size(); i++)
    {
  int j = i;
  Pet tp = array.get(i);
  String B = array.get(i).getName();
      while ((j > 0) && (array.get(j-1).getName().compareTo(B) > 0 ))
      {
    array.set(j, array.get(j-1));
    j--;
      }
  array.set(j,tp);
    }
  }
}

Answer 3

Pet p = new Pet(nam);,Pet类没有接受任何参数的构造函数。