how to intentionally corrupt a file in java

Note: Please do not judge this question. To those who think that I am doing this to "cheat"; you are mistaken, as I am no longer in school anyway. I took on this project because I thought it might be fun. Before you down-vote, please consider the value of the question it's self, and not the speculative uses of it, as the purpose of SO is not to judge, but simply give the public information.

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I am developing a program in java that is supposed intentionally corrupt a file (specifically a .doc, txt, or pdf, but others would be good as well) The purpose of this project is for students who want to get extra time on assignments, so they create a corrupt file, and send that in first (similar to this)

I initially tried this:

public void corruptFile (String pathInName, String pathOutName) {
     curroptMethod method  = new curroptMethod();
     ArrayList<Integer> corruptHash = corrupt(getBytes(pathInName));
     writeBytes(corruptHash, pathOutName);
     new MimetypesFileTypeMap().getContentType(new File(pathInName));
     //  "/home/ephraim/Desktop/testfile"
 }
 
 public ArrayList<Integer> getBytes(String filePath) {
     ArrayList<Integer> fileBytes = new ArrayList<Integer>();
     try {
         FileInputStream myInputStream = new FileInputStream(new File(filePath));
         do {
             int currentByte = myInputStream.read();
             if(currentByte == -1) {
                 System.out.println("broke loop");
                 break;
             }
             fileBytes.add(currentByte);
         } while (true);
     } catch (FileNotFoundException e) {
         // TODO Auto-generated catch block
         e.printStackTrace();
     } catch (IOException e) {
         // TODO Auto-generated catch block
         e.printStackTrace();
     }
     System.out.println(fileBytes);
     return fileBytes;
 }
 
 public void writeBytes(ArrayList<Integer> hash, String pathName) {
     try {
         OutputStream myOutputStream = new FileOutputStream(new File(pathName));
         for (int currentHash : hash) {
             myOutputStream.write(currentHash);
         }
     } catch (FileNotFoundException e) {
         // TODO Auto-generated catch block
         e.printStackTrace();
     } catch (IOException e) {
         // TODO Auto-generated catch block
         e.printStackTrace();
     }
     //System.out.println(hash);
 }
 
 public ArrayList<Integer> corrupt(ArrayList<Integer> hash) {
     ArrayList<Integer> corruptHash = new ArrayList<Integer>();
     ArrayList<Integer> keywordCodeArray = new ArrayList<Integer>();
     Integer keywordIndex = 0;
             String keyword = "corruptthisfile";
 
     for (int i = 0; i < keyword.length(); i++) {
         keywordCodeArray.add(keyword.codePointAt(i));
     }
 
     for (Integer currentByte : hash) {
 
 
         //Integer currentByteProduct = (keywordCodeArray.get(keywordIndex) + currentByte) / 2;
         Integer currentByteProduct =  currentByte - keywordCodeArray.get(keywordIndex);
         if (currentByteProduct < 0) currentByteProduct += 255;
         corruptHash.add(currentByteProduct);
 
         if (keywordIndex == (keyword.length() - 1)) {
             keywordIndex = 0;
         } else keywordIndex++;
     }
 
     //System.out.println(corruptHash);
     return corruptHash;
 }
 

but the problem is that the file is still openable. When you open the file, all of the words are changed (and they may not make any sense, and they may not even be letters, but it can still be opened)

so here is my actual question:

Is there a way to make a file so corrupt that the computer doesn't know how to open it at all (ie. when you open it, the computer will say something along the lines of "this file is not recognized, and cannot be opened")?

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