为什么此代码打印一个空字符串？

Question

I am trying to take a set of characters from a text file then store it in a string and print it. However when compile and run the file, it returns null.

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

public class ReadString
{
    public static void main(String[] args) throws FileNotFoundException, IOException
    {

    ReadString read = new ReadString();
    System.out.println(read.readFileTxt());   //Prints the string content read from input stream

    }   

    public String readFileTxt() throws FileNotFoundException, IOException
    {
    InputStream in = new FileInputStream(new File("test.txt"));
        BufferedReader reader = new BufferedReader(new InputStreamReader(in));
        StringBuilder out = new StringBuilder();
        String line;
            while ((line = reader.readLine()) != null) 
        {
            out.append(line);
            }

      //  reader.close();
    return line;
    }       
}

Answer 1

您返回的是最后一行（该行为null，因为它导致循环退出），而不是out.toString() 。

Answer 2

Your code returns the last line read from the file. You want to return out.toString() instead.