java - 无法在Java中打印出集合

Question

我正在编写一个程序，读取两个文本文件并找出差异但由于某种原因，我无法打印结果集。我检查了很多次还是没有找到原因，希望大家能帮帮我。这是代码。

问题出现在每个打印集的位置。

    import java.io.*;
    import java.util.*;

    public class PartOne {


    public static void readFileAtPath(String filePathOne, String filePathTwo) {
        // Lets make sure the file path is not empty or null
        if (filePathOne == null || filePathOne.isEmpty()) {
            System.out.println("Invalid File Path");
            return;
        }

        if (filePathTwo == null || filePathTwo.isEmpty()) {
            System.out.println("Invalid File Path");
            return;
        }

        Set<String> newUser = new HashSet<String>();
        Set<String> oldUser = new HashSet<String>();

        BufferedReader inputStream = null;
        BufferedReader inputStream2 = null;
        // We need a try catch block so we can handle any potential IO errors
        try {
            // Try block so we can use ‘finally’ and close BufferedReader
            try {
                inputStream = new BufferedReader(new FileReader(filePathOne));
                inputStream2 = new BufferedReader(new FileReader(filePathTwo));

                String lineContent = null;
                String lineContent2 = null;

                // Loop will iterate over each line within the file.
                // It will stop when no new lines are found.
                while ((lineContent = inputStream.readLine()) != null) {
                    // Here we have the content of each line.
                    // For now, I will print the content of the line.
                    // System.out.println("Found the line: " + lineContent);
                    oldUser.add(lineContent);
                }

                while ((lineContent2 = inputStream.readLine()) != null) {
                    newUser.add(lineContent2);
                }

                Set<String> uniqueUsers = new HashSet<String>(newUser);
                uniqueUsers.removeAll(oldUser);

            }
            // Make sure we close the buffered reader.
            finally {
                if (inputStream != null)
                    inputStream.close();
                if (inputStream2 != null)
                    inputStream2.close();
            }


            for (String temp : uniqueUsers) {
                 System.out.println(temp);
             }

        } catch (IOException e) {
            e.printStackTrace();
        }
    }// end of method

    public static void main(String[] args) {
        String filePath2 = "userListNew.txt";
        String filePath = "userListOld.txt";
        readFileAtPath(filePath, filePath2);

    }
}

Answer 1

你的问题是范围。您在 try block 内定义该集合，但随后尝试从该 block 外部访问它。您必须在要使用该变量的同一范围内定义所有变量。

将 uniqueUsers 的定义移至 try block 之前。

*编辑以回应您的评论。

您正在从同一输入流读取两次。第二个 while 循环应该从 inputStream2 读取。