JAVA:如何按字母顺序对从文件读取并输出到控制台的字符串进行排序？

Question

我想在控制台中按姓氏对从文件中读取的联系人进行排序？我该怎么做呢？联系人已写入从姓氏开始的文件中，当用户想要在控制台中查看联系人时，我只想按字母顺序将它们读回到应用程序中。

// Read from file, print to console. by XXXXX
            // ----------------------------------------------------------
            int counter = 0;
            String line = null;

            // Location of file to read
            File file = new File("contactlist.csv");

            try {

                Scanner scanner = new Scanner(file);

                while (scanner.hasNextLine()) {
                    line = scanner.nextLine();
                    System.out.println(line);
                    counter++;
                }
                scanner.close();
            } catch (FileNotFoundException e) {

            }
            System.out.println("\n" + counter + " contacts in records.");

        }
        break;
        // ----------------------------------------------------------
        // End read file to console. by XXXX

Answer 1

在打印之前，将每一行添加到排序集中，如 TreeSet :

Set<String> lines = new TreeSet<>();
while (scanner.hasNextLine()) {
    line = scanner.nextLine();
    lines.add(line);
    counter++;
}

for (String fileLine : lines) {
    System.out.println(fileLine);
}