Java扫描器不会忽略换行（\\ n）

Question

I know that by default, the Scanner skips over whitespaces and newlines. There is something wrong with my code because my Scanner does not ignore "\\n".

For example: the input is "this is\\na test." and the desired output should be ""this is a test."

this is what I did so far:

Scanner scan = new Scanner(System.in);
String token = scan.nextLine();
String[] output = token.split("\\s+");
for (int i = 0; i < output.length; i++) {
    if (hashmap.containsKey(output[i])) {
        output[i] = hashmap.get(output[i]);
    }
    System.out.print(output[i]);
    if (i != output.length - 1) {
        System.out.print(" ");
    }

Answer 1

nextLine() ignores the specified delimiter (as optionally set by useDelimiter() ), and reads to the end of the current line.

Since input is two lines:

this is
a test.

only the first line ( this is ) is returned.

You then split that on whitespace, so output will contain [this, is] .

Since you never use the scanner again, the second line ( a test. ) will never be read.

In essence, your title is right on point: Java Scanner does not ignore new lines (\\n)
It specifically processed the newline when you called nextLine() .

Answer 2

You don't have to use a Scanner to do this

        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        String result = in.lines().collect(Collectors.joining(" "));

Or if you really want to use a Scanner this should also work

        Scanner scanner = new Scanner(System.in);
        Spliterator<String> si = Spliterators.spliteratorUnknownSize(scanner, Spliterator.ORDERED);
        String result = StreamSupport.stream(si, false).collect(Collectors.joining(" "));