Java's L number (long) specification

There are specific suffixes for long (e.g. 39832L), float (e.g. 2.4f) and double (e.g. -7.832d).

If there is no suffix, and it is an integral type (e.g. 5623), it is assumed to be an int. If it is not an integral type (e.g. 3.14159), it is assumed to be a double.

In all other cases (byte, short, char), you need the cast as there is no specific suffix.

The Java spec allows both upper and lower case suffixes, but the upper case version for longs is preferred, as the upper case L is less easy to confuse with a numeral 1 than the lower case l.

See the JLS section 3.10 for the gory details (see the definition of IntegerTypeSuffix).

By default any integral primitive data type (byte, short, int, long) will be treated as int type by java compiler. For byte and short, as long as value assigned to them is in their range, there is no problem and no suffix required. If value assigned to byte and short exceeds their range, explicit type casting is required.

Ex:

byte b = 130; // CE: range is exceeding.

to overcome this perform type casting.

byte b = (byte)130; //valid, but chances of losing data is there.

In case of long data type, it can accept the integer value without any hassle. Suppose we assign like

long l = 2147483647; //which is max value of int

in this case no suffix like L/l is required. By default value 2147483647 is considered by java compiler is int type. Internal type casting is done by compiler and int is auto promoted to Long type.

long l = 2147483648; //CE: value is treated as int but out of range 

Here we need to put suffix as L to treat the literal 2147483648 as long type by java compiler.

so finally

long l = 2147483648L;// works fine.

I hope you won't mind a slight tangent, but thought you may be interested to know that besides F (for float), D (for double), and L (for long), a proposal has been made to add suffixes for byte and short—Y and S respectively. This would eliminate to the need to cast to bytes when using literal syntax for byte (or short) arrays. Quoting the example from the proposal:

MAJOR BENEFIT: Why is the platform better if the proposal is adopted?

cruddy code like

 byte[] stuff = { 0x00, 0x7F, (byte)0x80,  (byte)0xFF};

can be recoded as

 byte[] ufum7 = { 0x00y, 0x7Fy, 0x80y, 0xFFy };

Joe Darcy is overseeing Project Coin for Java 7, and his blog has been an easy way to track these proposals.

These are literals and are described in section 3.10 of the Java language spec.

It seems like these would be good to have because (I assume) if you could specify the number you're typing in is a short then java wouldn't have to cast it

Since the parsing of literals happens at compile time, this is absolutely irrelevant in regard to performance. The only reason having short and byte suffixes would be nice is that it lead to more compact code.