Question

我被困在这个没有写入输出文件的部分

第一堂课是联系我我不得不修改这不是我的班级是作者班我只是不得不使用它

    //********************************************************************  
// Contact.java Author: Lewis/Loftus  
//  
// Represents a phone contact.  
//********************************************************************  
public class Contact implements Comparable  
{  
 private String firstName, lastName, phone;  
  //-----------------------------------------------------------------  
  // Constructor: Sets up this contact with the specified data.  
  //-----------------------------------------------------------------  
  public Contact (String first, String last, String telephone)  
  {  
    firstName = first;  
    lastName = last;  
    phone = telephone;  
  }  
  //-----------------------------------------------------------------  
  // Returns a description of this contact as a string.  
  //-----------------------------------------------------------------  
  public String toString ()  
  {  
    return lastName + ", " + firstName + "\t" + phone;  
  }  
  //-----------------------------------------------------------------  
  // Returns true if the first and last names of this contact match  
  // those of the parameter.  
  //-----------------------------------------------------------------  
  public boolean equals (Object other)  
  {  
   return (lastName.equals(((Contact)other).getLastName()) &&  
   firstName.equals(((Contact)other).getFirstName()));  
  }  
  //-----------------------------------------------------------------  
  // Uses both last and first names to determine ordering.  
  //-----------------------------------------------------------------  
  public int compareTo (Object other)  
  {  
   int result;  
   String otherFirst = ((Contact)other).getFirstName();  
   String otherLast = ((Contact)other).getLastName();  

   if (lastName.equals(otherLast))  

      result = firstName.compareTo(otherFirst);  
   else  

      result = lastName.compareTo(otherLast);  

    return result;  
  }  
  //-----------------------------------------------------------------  
  // First name accessor.  
  //-----------------------------------------------------------------  
  public String getFirstName ()  
  {  
    return firstName;  
  }  
  //-----------------------------------------------------------------  
  // Last name accessor.  
  //-----------------------------------------------------------------  
  public String getLastName ()  
  {  
    return lastName;  
  }  
}

这个课程的排序很好。它排序没有问题

    public class Sorting {  

    public static void bubbleSortRecursive(Comparable[] data, int n)   
    {  

        if (n < 2)   
        {  
            return;  
        }  
        else  
        {  

            int lastIndex = n - 1;  

            for (int i = 0; i < lastIndex; i++)   
            {  
                if (data[i].compareTo(data[i + 1]) > 0)   
                { //swap check  

                    Comparable tmp = data[i];  
                    data[i] = data[i + 1];  
                    data[i + 1] = tmp;  
                }  
            }  

            bubbleSortRecursive(data, lastIndex);  
        }  
    }  

    public static void selectionSortRecursive(Comparable[] data, int n)   
    {  

        if (n < 2)   
        {  
            return;  
        }   
        else   
        {  

            int lastIndex = n - 1;  
            int largestIndex = lastIndex;  

            for (int i = 0; i < lastIndex; i++)   
            {  
                if (data[i].compareTo(data[largestIndex]) > 0)   
                {  
                    largestIndex = i;  
                }  
            }  

            if (largestIndex != lastIndex)   
            { //swap check  
                Comparable tmp = data[lastIndex];  
                data[lastIndex] = data[largestIndex];  
                data[largestIndex] = tmp;  
            }  

            selectionSortRecursive(data, n - 1);  
        }  
    }  
}

这是我需要帮助的部分。它没有输出到p4output.txt，我不知道问题是什么。

    import java.io.BufferedWriter;  
import java.io.File;  
import java.io.FileWriter;  
import java.io.IOException;  


public class TestProject4 {  

    public static void main(String[] args)   
    {  

        doBubbleSortRecursive();  

        System.out.println();  
        System.out.println();  

        doSelectionSortRecursive();  

    }  
    private static void doBubbleSortRecursive()  
    {  
        Contact[] contacts = createContacts();  

        System.out.println("Before bubbleSortRecursive(): ");  
        for (int i=0; i<contacts.length; i++)  
        System.out.println(contacts[i].toString());  


        Sorting.bubbleSortRecursive(contacts, contacts.length);  

        System.out.println("\nAfter bubbleSortRecursive(): ");  
        for (int i=0; i<contacts.length; i++)  
        System.out.println(contacts[i].toString());  
    }  

    private static void doSelectionSortRecursive()   
    {  
        Contact[] contacts = createContacts();  


        System.out.println("Before selectionSortRecursive(): ");  
        for (int i=0; i<contacts.length; i++)  
        System.out.println(contacts[i].toString());  

        Sorting.selectionSortRecursive(contacts, contacts.length);  

        System.out.println("\nAfter selectionSortRecursive(): ");  
        for (int i=0; i<contacts.length; i++)  
        System.out.println(contacts[i].toString());  
    }  

    private static void printContacts(Contact[] contacts)  
    {  

        try   
        {  

        // this part I need help with it is not outputing in the text file   
                    File file = new File("p4output.txt");  
            FileWriter fw = new FileWriter(file.getAbsoluteFile());  
            BufferedWriter bw = new BufferedWriter(fw);  

            for (Contact contact : contacts)  
             {  
                bw.write(contact.toString());       
             }              
              bw.close();  
        }  

        catch (IOException e)   
        {  
           e.printStackTrace();  
        }  

       System.out.println("\t" + contacts);  
    }  
    public static Contact[] createContacts()   
    {  
        return new Contact[]   
        {  
            new Contact("John"  , "Smith" , "610-555-7384"),  
            new Contact("Sarah" , "Barnes"   , "215-555-3827"),  
            new Contact("Mark"  , "Riley", "333-333-3333"),  
            new Contact("Laura"   , "Getz"  ,"663-555-3984"),  
            new Contact("Larry"  , "Smith"  , "464-555-3489"),  
            new Contact("Frank"  , "Phelps" , "322-555-2284"),  
            new Contact("Mario"    , "Guzman" , "804-555-9066"),  
            new Contact("Marsha"    , "Grant" , "243-555-2837"),  
        };  
     }  
 }

Answer 1

根据Eclipse，你永远不会调用/使用printContacts(Contact[] contacts);方法

enter image description here

您的printContacts(Contact[] contacts);包含写入文件的语句。

Answer 2

您似乎没有在程序中调用函数printContacts（）。在创建联系人和排序后尝试调用它。

可能看起来像这样：

public static void main(String[] args)   
{  

    doBubbleSortRecursive();  

    System.out.println();  
    System.out.println();  

    doSelectionSortRecursive();  
    printContacts(contactArray);//inserted code
}

此外，当您调用排序方法doSelectionSortRecursive（）时，您不会返回联系人列表。为它创建一个return语句，然后将contact数组放入printContacts函数中。

以下是一个例子：

public static void main(String[] args)   
{  

    doBubbleSortRecursive();  

    System.out.println();  
    System.out.println();  

    Contact[] contacts = doSelectionSortRecursive();  
    printContacts(contacts);
}  

public static Contact[] doSelectionSortRecursive(){
    Contact[] contacts = createContacts();
    //your sorting code
    return contacts;
}

使用此方法可以在方法排序后从方法中获取联系人数组。

在输出文件上写

2 个答案: