[JAVA] How to read a file and treat it as standard input

It was troublesome to enter it for the test, so I was wondering if it could be done. As a result of investigation, by specifying ** FileInputStream ** that implements InputStream as the standard input It seems that it can be realized, so I wrote the code.


try {
    InputStream stream = new FileInputStream("filename");
    System.setIn(new FileInputStream(stream);
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    String str = br.readLine();
     *Description of other data processing, etc.
} catch (IOException e) {


I felt that it wasn't so when asked if there was another opportunity to use it. Generally, the file is read and processed normally.

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