Java I/O

Numeric Data

Input streams read bytes and output streams write bytes. Readers read characters and writers write characters. Therefore, to understand input and output, you first need a solid understanding of how Java deals with bytes, integers, characters, and other primitive data types, and when and why one is converted into another. In many cases Java’s behavior is not obvious.

Integer Data

The fundamental integer data type in Java is the int , a four-byte, big-endian, two’s complement integer. An int can take on all values between -2,147,483,648 and 2,147,483,647. When you type a literal integer like 7, -8345, or 3000000000 in Java source code, the compiler treats that literal as an int. In the case of 3000000000 or similar numbers too large to fit in an int, the compiler emits an error message citing “Numeric overflow.”

longs are eight-byte, big-endian, two’s complement integers with ranges from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807. long literals are indicated by suffixing the number with a lower- or uppercase L. An uppercase L is preferred because the lowercase l is too easily confused with the numeral 1 in most fonts. For example, 7L, -8345L, and 3000000000L are all 64-bit long literals.

There are two more integer data types available in Java, the short and the byte . shorts are two-byte, big-endian, two’s complement integers with ranges from -32,768 to 32,767. They’re rarely used in Java and are included mainly for compatibility with C.

bytes, however, are ...