FAQ: Input and Output: Lesson - FileInputStream

This community-built FAQ covers the “FileInputStream” exercise from the lesson “Input and Output: Lesson”.

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FAQs on the exercise FileInputStream

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I assume that this sets i to be the next integer read from the file, and then checks whether that integer is not -1.

    while((i = inputFile.read()) != -1) {    
      System.out.print((char)i);
      j++; 
    }

which would be the same as doing:

    i = inputFile.read();
    while(i != -1) {
      System.out.print((char)i);
      i = inputFile.read();
    }

How would I read to contents of a file into a string?

The best I could do was:

    FileInputStream inStream = new FileInputStream(path);
    int i = 0;
    int j = 0;
    
    // get length first
    while((i = inStream.read()) != -1) {    
      j++; 
    }
    inStream.close();
    //j++;
    // j is the length
    
    // make an array of chars
    char[] charray = new char[j];
    FileInputStream inStream2 = new FileInputStream(path);
    for (int k = 0; k < j; k++) {
      i = inStream2.read();
      charray[k] = (char)i;  // error? since i can be negative?
    }
    inStream2.close();
    // make the array into a string
    String str = new String(charray);

I guess the assumption is that characters are encoded as one byte in the text file (UTF-8 or ASCII or something like that).

EDIT: I found a constructor for strings that uses bytes, so I guess its better to use that here.

modified code
    FileInputStream inStream = new FileInputStream(path);
    int i = 0;
    int j = 0;
    
    // get length first
    while((i = inStream.read()) != -1) {    
      j++; 
    }
    inStream.close(); 
    // j is the length
    
    // make an array of bytes
    byte[] bytes = new byte[j];
    FileInputStream inStream2 = new FileInputStream(path);
    for (int k = 0; k < j; k++) {
      i = inStream2.read();
      bytes[k] = (byte)i; // warning?
      // conversion warning because bytes use less space than ints?
    }
    inStream2.close();
    // make the array into a string
    String str = new String(bytes);