确定java中InputStream中下一次读取的类型

Question

Assuming that there is a file with a set of primitives written in it, however I do not know the type of primitives.

How can I read the data into the appropriate data type from my code? (that is read int into int, byte into byte etc)

Or is this impossible?

Answer 1

You can try to convert it to a desired type ... if the conversion fails you try the next type and so on. The final type being a String.

For example if the file would hold those lines:

1
1.3
12345324223423
test
true
false

You can test each value if it can be converted:

try {
    int value = Integer.parseInt(test);
}
catch (NumberFormatException e) {

    try {

        double value2 = Double.parseDouble(test);
    }
    catch (NumberFormatException ex) {

            ... and so on ... 
    }
}

I would start with the smallest and go to bigger, for instance:

• Byte
• Integer
• Long
• BigDecimal
• Boolean
• Char
• and last String