使用DataInputStream java检查文件中的下一个数据类型是什么？

Question

I am trying to read in the contents of a file byte by byte individually. TO do this, I'm using the DataInputStream 's readByte() method. However, after I do this, I need to see if the byte it read in was originally a char or an int so I can store it appropriately. So basically, when reading a file I need to be able to check what the next character's primitive datatype is before converting it to a byte to read. Alternativly, I could somehow check the next character before I read it in, then if it's an int use readInt() or if its a char use readChar(). Here is my current code:

public class Lexer {
    public static void main(String a[]) {
        try {
            File file = new File("placeholder.txt"); 
            DataInputStream is = new DataInputStream(new FileInputStream(file));
            char c;
            int i;
            byte b;

            while((b = is.readByte()) != -1) {
                //here, I would like to now store my byte to c, or i based on what type it
                // originally was. 

            }
        } catch(FileNotFoundException e) {
            System.out.println("Fatal Error: Could not find program source code file");
        } catch (IOException e) {
            System.out.println("Fatal Error: Could not i/o with source code file");
        }


    }   
    //}
}

File Contents:

javarocks1234! //while reading, I need to know if the next byte I read in was a char or an int in this file 

Answer 1

you can try something like,

String readtxt = "9999"; // reading string from file
java.util.regex.Pattern numberPatter = java.util.regex.Pattern.compile(".*[^0-9].*");

if( numberPatter .matcher(readtxt).matches() )
    System.out.println("it's numeric");
else
    System.out.println("It's not a numeric");