很难查明第 71 行出现的错误。我需要从文本文件中读取数据,将数据收集到一些树形图中,以便稍后在两个输出文件中对其进行修改。我有一个 while 循环,它通过将文本置于大写形式来修改数据,然后将数据拆分为每行的一个数组,然后将该数组数据放入 3 个树形图中。错误是 NullPointerException,当我注释掉该行时,它会将其抛出到另一行,因此我的循环显然有问题,我只是看不到它。该循环似乎只运行一次,无法遍历所有行,因此如果文本文件有 5 行,它将读取 4 行,给出正确的值,然后抛出错误。我尝试修改文本文件的内容,但没有成功。我尝试修改 while 循环,也无济于事。任何指示将不胜感激。文本文件如下所示:
110001 commercial 500000.00 101
110223 residential 100000.00 104
110020 commercial 1000000.00 107
550020 land 400000.00 105
错误代码如下:
java.lang.NullPointerException
at realestate.RealEstate.main(RealEstate.java:71)
这是我到目前为止的代码:
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package realestate;
import java.io.BufferedReader;
import java.io.*;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.PrintWriter;
import static java.lang.System.out;
import java.nio.file.DirectoryNotEmptyException;
import java.nio.file.Files;
import java.nio.file.NoSuchFileException;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Scanner;
import java.util.Set;
import java.util.TreeMap;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
*
*
*/
public class RealEstate {
/**
* @param args the command line arguments
* @throws java.io.IOException
*/
public static void main(String[] args) throws IOException {
Scanner input = new Scanner(System.in);//Prompt user for listings.txt location.
String listInput = null;
System.out.print("Please enter the real estate listings.txt file's full path: ");
listInput = input.next();
if(listInput.contains("listings.txt") == false) {//Verify input with if else statement.
System.out.print("\nSorry, the path entered will not work. Please enter the full path to listings.txt: ");
listInput = input.next();
if(listInput.contains("listings.txt") == true){//Nested in order to display same message.
System.out.print("\nThank you, the agentreport.txt file is now available.");
}
} else {
System.out.print("\nThank you, the agentreport.txt file is now available.\n");
}
String[][] listArray; //Initialize array for later data manipulation.
listArray = new String[10][5];
listArray = null;
Path ar = Paths.get("D:\\JAVA\\RealEstate\\agentreport.txt");//Deletes agentreport.txt if it already exists.
try {
Files.deleteIfExists(ar);
} catch (IOException x) {
System.out.print("\nIO Exception, please try again.");
}
//Reads listings.txt, parses information, places data in array, then inside treemaps.
BufferedReader br = null;
String[] lineArray = new String[4];
TreeMap tm1 = new TreeMap();
TreeMap tm2 = new TreeMap();
TreeMap tm3 = new TreeMap();
try {
br = new BufferedReader(new FileReader(listInput));
String line = br.readLine();
while(line != null){//WHERE I"M GETTING ERROR
line = br.readLine();//Read line.
line = line.toUpperCase();//Make everything uppercase.
lineArray = line.split("\\s+");//Place line into new array based on where spaces are.
tm1.put(lineArray[0], lineArray[1]);//Place array items into treemaps.
tm2.put(lineArray[0], lineArray[2]);
tm3.put(lineArray[0], lineArray[3]);
System.out.print(tm1 + "\n" + tm2 + "\n" + tm3 + "\n");//Test if data is received correctly.
lineArray = null;//Clear array for next line.
}
} catch (NullPointerException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
System.out.print("\nIO Exception, please try again.");
}
try {//File writer, creates file agentreport.txt and starts writing.
File arFile = new File("D:\\JAVA\\RealEstate\\agentreport.txt");
FileOutputStream is = new FileOutputStream(arFile);
OutputStreamWriter osw = new OutputStreamWriter(is);
Writer w = new BufferedWriter(osw);
//w.write();//what I need the writer to do
//w.close();
} catch (FileNotFoundException e) {
System.err.println("Problem writing to the file, agentreport.txt");
}
}
}
提前致谢!
最佳答案
改变
br = new BufferedReader(new FileReader(listInput));
String line = br.readLine();
while(line != null){//WHERE I"M GETTING ERROR
到
br = new BufferedReader(new FileReader(listInput));
String line = null;
while((line=br.readLine()) != null){//WHERE I"M GETTING ERROR
当您在循环内使用br.readLine();
时,它仍然可以获得null
。所以你需要在条件检查之前使用它
附注
在您的代码中,您跳过第一行。我的代码也会解决这个问题
关于java - 在 while 循环内使用 bufferedreader 时获取 NullPointerException,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/23349581/