Literals

A literal is the source code representation of a fixed value; literals are represented directly in your code without requiring computation. As shown below, it’s possible to assign a literal to a variable of a primitive type:

There several types of literals including:

  • Integer Literals
  • Floating-Point Literals
  • Character and String Literals

Integer Literals

An integer literal is of type long if it ends with the letter L or l; otherwise it is of type int. It is recommended that you use the upper case letter L because the lower case letter l is hard to distinguish from the digit 1.

Values of the integral types byte, short, int, and long can be created from int literals. Values of type long that exceed the range of int can be created from long literals. Integer literals can be expressed by these number systems:

  • Decimal: Base 10, whose digits consists of the numbers 0 through 9; this is the number system you use every day
  • Hexadecimal: Base 16, whose digits consist of the numbers 0 through 9 and the letters A through F
  • Binary: Base 2, whose digits consists of the numbers 0 and 1 (you can create binary literals in Java SE 7 and later)

Run The Application

Right click to the IntergerLiteral class; select Run As -> Java Application.

Output

The output value for  decVal, hexVal, binVal using System.out.println() are the same and it’s 26.

Floating-Point Literals

A floating-point literal is of type float if it ends with the letter F or f; otherwise its type is double and it can optionally end with the letter D or d.

The floating point types (float and double) can also be expressed using E or e (for scientific notation), F or f (32-bit float literal) and D or d (64-bit double literal; this is the default and by convention is omitted).

Run The Application

Right click to the FloatingPoint class; select Run As -> Java Application.

Output

As you can see, outputs are all same regardless the format of the variables. In order to display in correct forms of numbers; we can use System.out.format() method or java.text.DecimalFormat class… that’ll be discussed later.

Character and String Literals

Literals of types char and String may contain any Unicode (UTF-16) characters. If your editor and file system allow it, you can use such characters directly in your code. If not, you can use a “Unicode escape” such as '\u0108' (capital C with circumflex), or "S\u00ED Se\u00F1or" (Sí Señor in Spanish). Always use ‘single quotes’ for char literals and “double quotes” for String literals. Unicode escape sequences may be used elsewhere in a program (such as in field names, for example), not just in char or String literals.

The Java programming language also supports a few special escape sequences for char and String literals: \b (backspace), \t (tab), \n (line feed), \f (form feed), \r (carriage return), \" (double quote), \' (single quote), and \\ (backslash).

There’s also a special null literal that can be used as a value for any reference type. null may be assigned to any variable, except variables of primitive types. There’s little you can do with a null value beyond testing for its presence. Therefore, null is often used in programs as a marker to indicate that some object is unavailable.

Finally, there’s also a special kind of literal called a class literal, formed by taking a type name and appending “.class"; for example, String.class. This refers to the object (of type Class) that represents the type itself.

Using Underscore Characters in Numeric Literals

In Java SE 7 and later, any number of underscore characters (_) can appear anywhere between digits in a numerical literal. This feature enables you, for example. to separate groups of digits in numeric literals, which can improve the readability of your code.

For instance, if your code contains numbers with many digits, you can use an underscore character to separate digits in groups of three, similar to how you would use a punctuation mark like a comma, or a space, as a separator.

The following example shows other ways you can use the underscore in numeric literals:

Run The Application

Right click to the UderscoreInNumber class; select Run As -> Java Application.

Output

You can place underscores only between digits; you cannot place underscores in the following places:

  • At the beginning or end of a number
  • Adjacent to a decimal point in a floating point literal
  • Prior to an F or L suffix
  • In positions where a string of digits is expected

The following examples demonstrate valid and invalid underscore placements (which are highlighted) in numeric literals. Eclipse IDE will show compilation error message: “Underscores have to be located within digits”