How to read a single word (or line) from a text fi

问题:

Like the title says, im trying to write a program that can read individual words from a text file and store them to String variables. I know how to use a FileReader or FileInputStream to read a single char but for what I'm trying to this wont work. Once I input the words I am trying to compare these with other String variables in my program using .equals so it would be best if I can import as Strings. I am also okay with inputting an entire line from a text file as a String in which case Ill just put one word on each line of my file. How do I input words from a text file and store them to String variables?

EDIT: Okay, that duplicate sort of helps. It might work for me but the reason my question is a little different is because the duplicate only tells how to read a single line. Im trying to read the individual words in the line. So basically splitting the line String.

回答1:

To read lines from a text file, you can use this (uses try-with-resources):

String line;

try (
    InputStream fis = new FileInputStream("the_file_name");
    InputStreamReader isr = new InputStreamReader(fis, Charset.forName("UTF-8"));
    BufferedReader br = new BufferedReader(isr);
) {
    while ((line = br.readLine()) != null) {
        // Do your thing with line
    }
}

More compact, less-readable version of the same thing:

String line;

try (BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream("the_file_name"), Charset.forName("UTF-8")))) {
    while ((line = br.readLine()) != null) {
        // Do your thing with line
    }
}

To chunk a line into individual words, you can use String.split:

while ((line = br.readLine()) != null) {
    String[] words = line.split(" ");
    // Now you have a String array containing each word in the current line
}

回答2:

These are all really complex answers. And I am sure they are all useful. But I prefer the elegantly simple Scanner :

public static void main(String[] args) throws Exception{
    Scanner sc = new Scanner(new File("fileName.txt"));
    while(sc.hasNext()){
        String s = sc.next();
        //.....
    }
}

回答3:

You must use StringTokenizer! here an example and read this String Tokenizer

private BufferedReader innerReader; 
public void loadFile(Reader reader)
        throws IOException {
    if(reader == null)
    {
        throw new IllegalArgumentException("Reader not valid!");
    }
        this.innerReader = new BufferedReader(reader);
    String line;
    try
    {
    while((line = innerReader.readLine()) != null)
    {
        if (line == null || line.trim().isEmpty())
            throw new IllegalArgumentException(
                    "line empty");
        //StringTokenizer use delimiter for split string
        StringTokenizer tokenizer = new StringTokenizer(line, ","); //delimiter is ","
        if (tokenizer.countTokens() < 4)
            throw new IllegalArgumentException(
                    "Token number not valid (<= 4)");
        //You can change the delimiter if necessary, string example
        /*
        Hello / bye , hi
        */
        //reads up "/"
        String hello = tokenizer.nextToken("/").trim();
        //reads up ","
        String bye = tokenizer.nextToken(",").trim();
        //reads up to end of line
        String hi = tokenizer.nextToken("\n\r").trim();
        //if you have to read but do not know if there will be a next token do this
        while(tokenizer.hasMoreTokens())
        {
          String mayBe = tokenizer.nextToken(".");
        }
    }
    } catch (Exception e) {
        throw new IllegalArgumentException(e);
    }
}

回答4:

In java8 you can do something like the following:

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.stream.Collectors;

public class Foo {
    public List<String> readFileIntoListOfWords() {
        try {
            return Files.readAllLines(Paths.get("somefile.txt"))
                .stream()
                .map(l -> l.split(" "))
                .flatMap(Arrays::stream)
                .collect(Collectors.toList());
        }
        catch (IOException e) {
            e.printStackTrace();
        }
        return Collections.emptyList();
    }
}

Though I suspect that the argument to split may need to be changed, eg to trim punctuation from the end of a word