java-子序列词

假设这是我的.txt文件ABCDBCD和我想用的。子字符串：ABC BCD CDB DBC BCD

我怎样才能做到这一点？我还需要停止程序，因为一行少于3个字符。

static void lesFil(String fil, subsekvens allHashMapSubsequences) throws FileNotFoundException{
    Scanner scanner = new Scanner(new File("File1.txt"));
    String currentLine, subString;

    
    

        while(scanner.hasNextLine()){
            currentLine = scanner.nextLine();
            currentLine = currentLine.trim();

            for (int i = 0; i +  subSize <= currentLine.length(); i++){
    
                subString = currentLinje.substring(i, i + subSize);
                subSekStr.putIfAbsent(subString, new subsequence(subString));
            }
        }
    
   

    scanner.close();