java.lang.Error：未解决的编译问题：

Question

/* 使用属性列表的简单电话号码数据库 */

我已经在 Eclipse 中多次运行这个程序，但这向我展示了未解决的编译问题

package phoneBook;

import java.io.*;

import java.io.File;

import java.util.Properties;

class meths

{       

    BufferedReader br=new BufferedReader(new InputStreamReader(System.in));

    FileInputStream fin=null;

    try {

        fin=new FileInputStream("PhoneBook.txt");

    }catch(FileNotFoundException e)

    {

        e.printStackTrace();

    }

    String name,number;

    Properties pr=new Properties();

    if(fin!=null)

    {

        try {

            pr.load(fin); fin.close();

        }catch(FileNotFoundException e)

        {

            e.printStackTrace();

        }

    }

    void find() throws IOException

    {       

        System.out.println("Enter name to find number");

        name=br.readLine();

        System.out.println("Number is:"+pr.getProperty(number));

    }

    void enter()

    {

        FileOutputStream fout=new FileOutputStream("PhoneBook.txt");

        System.out.println("Enter name and number:");

        name=br.readLine();number=br.readLine();

        pr.put(name, number);

        pr.store(fout, "Phone Boook");

    }

     void operation()

        {   

            BufferedReader br=new BufferedReader(new InputStreamReader(System.in));

            int opt=0;

            System.out.println("1 for stop operation\n2 for enter new entry\n3 for searching number");

            while(opt!=1)

            {

                // Reading option

                try {

                    opt=br.read();

                } catch (IOException e) {

                    e.printStackTrace();

                }// Read opearation is complete

                switch(opt)

                {

                case 2: enter();    break;

                case 3: find();     break;

                }

            }

        }

}

public class PhoneBook 

{

    public static void main(String args[]) throws Exception

    {``

        meths ph=new meths();

        ph.operation();

    }

}

Answer 1

这是一个可能的更正：package phoneBook;import java.io.*;import java.util.Properties;class meths { BufferedReader br; FileInputStream fin; String name, number; Properties pr; File file; String path = "D:/PhoneBook.txt"; public meths() {    file = new File(path);    pr = new Properties();    br = new BufferedReader(new InputStreamReader(System.in));    //If file doesn't exist, create it and load it    if (!(file.exists() && file.canRead())){        try {            file.createNewFile();        } catch (IOException e) {            System.out.println("File can't be created");        }    }        try {            fin = new FileInputStream(file);        } catch (FileNotFoundException e) {            System.out.println("File can't be read");        }    // If file is not empty, load properties    if (fin != null) {        try {            pr.load(fin);            fin.close();        } catch (IOException e) {            System.out.println("Properties not loaded");        }     }  } void find() throws IOException {    System.out.println("\n>Enter name to find number:");    name = br.readLine();    System.out.println("Number is: " + pr.getProperty(name)); } void enter() throws IOException {    System.out.println("\n>Enter the name :");    name = br.readLine();    System.out.println("\n>Enter the number :");    number = br.readLine();    FileOutputStream fout = new FileOutputStream(file);    pr.put(name, number);    pr.store(fout, "Phone Boook"); } void choice() throws IOException {    System.out.println("\n>Enter your choice :"); } public boolean isInteger(String chaine) {    try {        Integer.parseInt(chaine);    } catch (NumberFormatException e) {        return false;    }    return true;  }void operation() throws IOException {    int opt = 0;    System.out.println("1 for stop operation\n2 for enter new entry\n3 for searching number\n");    while (opt != 1) {        choice();        String value = br.readLine();        if (isInteger(value)) {            opt = Integer.parseInt(value);            switch (opt) {            case 2:                enter();                break;            case 3:                find();                break;            }         }      }   } } public class PhoneBook {  public static void main(String args[]) throws Exception {    meths ph = new meths();    ph.operation();  }}控制台视图：文件 ：总之，我想说你必须学习基础知识才能理解类、构造函数、方法和成员的工作原理。