Variable Assignment in Java

When you assign a value to a variable in Java, the value is written directly in your source code. Such a written value is called a literal. A variable can only receive a value that the compiler can recognize, so the way you spell a value is not a cosmetic choice. Spelling tells Java what kind of value you mean.

A common first assumption is that a character is written exactly as it appears. You might expect the letter A to be written as A, or the asterisk as *. In Java that assumption creates ambiguity. A without quotation marks can be read as an identifier, which is a name such as a variable or method, and * can be read as the multiplication operator. Java therefore uses single quotation marks to say that you mean a character literal.

Follow what happens when the compiler reads a character literal. It sees an opening single quotation mark, then one character, then a closing single quotation mark. Those three parts together form a single char value. The quotation marks are not stored as part of the value. They are the signal that tells Java to treat the content as a character rather than as a name or an operator.

The comparison shows the key point. Single quotes build a char literal. Double quotes build a different kind of literal. Where Java expects a char, a double-quoted A does not satisfy that expectation, so the compiler rejects it. Keep this in mind whenever you write a single character value.

Some characters cannot be typed directly inside single quotes in a readable way, and some characters already have a meaning in Java syntax. For these, Java uses a backslash escape. The backslash does not stand alone. It combines with the character that follows it to form one character value. For example, the two-character sequence backslash followed by n represents a single newline character inside a char literal.

The escape sequences used in this article are the ones the source highlights: a backslash n for newline, a backslash followed by a single quotation mark for a single quote inside a char literal, and a double backslash for a literal backslash. Each of these uses two characters in the source code but produces one char value.

Java numeric literals are not limited to ordinary decimal notation. A number may appear as a regular integer, as a decimal real number, as an exponential expression, or as a value written in another number base. The spelling supplies information about how Java should interpret the literal. Read the literal's shape as a set of clues: a decimal point, an exponent, a suffix, or a prefix each signals something about its type.

The source names the three base indicators directly: a leading 0 indicates octal, 0x indicates hexadecimal, and 0b indicates binary. Decimal points and exponents indicate real-number literals, which Java treats as floating-point values. Integer literals have neither a decimal point nor an exponent.

Sometimes the default reading of a literal is not the type you need. A suffix placed at the end of a numeric literal tells Java which type to use. The L suffix marks a literal as long, and the f suffix marks a literal as float. The suffix is part of the literal's spelling, so it is one of the clues the source describes when it says that suffixes are read as type-related information.