如何在 java 中打印整行文本（来自输入文件）

Question

I'm trying to print each individual line of an external file, but I can only manage to print each individual word . Here's what my code currently looks like:

  Scanner scnr = new Scanner(System.in);
  System.out.println("Enter input filename: ");
  String inputFile = scnr.next();
  
  FileInputStream fileByteStream = null;
  Scanner inFS = null; 
  
  fileByteStream = new FileInputStream(inputFile);
  inFS = new Scanner(fileByteStream);
  
  while (inFS.hasNext()) {
     String resultToPrint = inFS.next();
     System.out.println(resultToPrint);
  }

So, for example, if the external.txt file is something like this: THIS IS THE FIRST LINE. (new line) THIS IS THE SECOND LINE. (new line) THIS IS THE THIRD LINE. ...

Then right now it prints like this: THIS (new line) IS (new line) THE (new line) FIRST (new line) LINE (new line) THIS (new line) IS...

and I want it to print like how it appears in the original file.

Any suggestions on how to make each iteration of resultToPrint be a full line of text, as opposed to a single word? (I'm new to java, so sorry if the answer seems obvious!)

Answer 1

In order to read a file you need a BufferedReader :

Reads text from a character-input stream, buffering characters so as to provide for the efficient reading of characters, arrays, and lines.

Then use it's method readLine :

Reads a line of text. A line is considered to be terminated by any one of a line feed ('\n'), a carriage return ('\r'), or a carriage return followed immediately by a linefeed.

This code reads every line of a file then prints it:

try (BufferedReader br = new BufferedReader(new FileReader(new File(filePath)))) {
  while ((line = br.readLine()) != null) {
    System.out.println(line);
  }
}

Answer 2

Replace the line

inFS = new Scanner(fileByteStream);

by

inFS = new Scanner(fileByteStream).useDelimiter( "\\n" );

This will set the "word" separator to the line feed character, making the full line a single "word".

Or use java.nio.files.Files.lines() …

Also java.io.BufferedReader.lines() would be a nice alternative …

Answer 3

Simpler and cleaner approach would be:

FileInputStream fis = new FileInputStream("filename");
Scanner sc = new Scanner(fis);
while (sc.hasNextLine()) {
    System.out.println(sc.nextLine());
}

or

BufferedReader br = new BufferedReader(new FileReader("filename"));
br.lines().forEach(System.out::println);