Java - 如何读取同一行中包含 Int 和字符串的文本文件

Question

如果文本文件包含

1 Apple
2 Banana
3 Orange
4 Carrot
5 Lemon
6 Lime
7 Mango 

如何读取文件以将第 4 行 carrot 的内容存储到一个变量中，将第 6 行 Lime 的内容存储到一个单独的变量中？

    //Get data from file
    String fruit = "";
    String greenFruit = "";


    FileReader file = new FileReader("my/file/path.txt");
    BufferedReader reader = new BufferedReader(file);

    System.out.println(fruit);
    System.out.println(greenFruit);

最终结果是这样的

"Fruit number 5 is a Lemon and Fruit Number 6 is a Lime"

Answer 1

尝试这样的事情：

String line = "";
String[] tokens;
int number;
String name;

while((line = reader.readLine()) != null)
{
    tokens = line.split(" ");

    // Use the following if you would rather split on whitespace for tab separated data
    // tokens = line.split("\\s+");

    number = Integer.parseInt(tokens[0]);
    name = tokens[1];

    System.out.println("Fruit number " + number + " is a " + name + "."
}

阅读String.split()方法。

Answer 2

我们可以使用 java NIO api 从文件中读取所有行，

    private static final Pattern SPACE = Pattern.compile(" ");

public static void main(final String[] args) throws URISyntaxException, IOException {
    final String output =
        Files.readAllLines(Paths.get(FileParser.class.getClassLoader().getResource("input.txt").toURI()))
            .stream()
            .map(SPACE::split)
            .map(it -> new Fruit(it[0], it[1]))
            .map(Fruit::toString)
            .collect(Collectors.joining(" and "));

    System.out.println(output);
   }
}

class Fruit {
 private final String number;
 private final String name;

Fruit(final String number, final String name) {
    this.number = number;
    this.name = name;
}

@Override
public String toString() {
    return "Fruit number ".concat(String.valueOf(number)).concat(" is a ").concat(name);
}
}

Output 将如下所示，

Fruit number 1 is a Apple and Fruit number 2 is a Banana and Fruit number 3 is a Orange and Fruit number 4 is a Carrot and Fruit number 5 is a Lemon and Fruit number 6 is a Lime and Fruit number 7 is a Mango

Answer 3

您可以使用Scanner阅读并检查是否有更多使用hasNext()

        FileReader file = new FileReader("file");
        Scanner scanner = new Scanner(file);
        while (scanner.hasNext()) {
            int number = scanner.nextInt();
            String name = scanner.next();
        }
        scanner.close();

Answer 4

Java 8款：

// normal solution
try (Stream<String> stream = Files.lines(Paths.get(fileName))) {
        stream.foreach(line -> {
           tokens = line.split(" ");

           number = Integer.parseInt(tokens[0]);
           name = tokens[1];
           System.out.println("Fruit number " + number + " is a " + name + "."
        });

        } catch (IOException e) {
            e.printStackTrace();
        }


// more OOP style
public class Fruit {
  private int number;
  private String name;

  public Fruit(String line) {
     String[] line = line.split(" ");
     this.number = Integer.parseInt(line[0]);
     this.name = line[1];
  }  
}
List<Fruit> list = new ArrayList;
try (Stream<String> stream = Files.lines(Paths.get(fileName))) {
            //1. convert all content to a object
            //2. convert it into a List
            list = stream
                    .map(Fruit::new)
                    .collect(Collectors.toList());

        } catch (IOException e) {
            e.printStackTrace();
        }

// then you can loop the list get what you want