Variable Names - Java Tutorial 5.0 英文版

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Variable Names

A program refers to a variable's value by the variable's name. For example, when it displays the value of the largestByte variable, the MaxVariablesDemo program uses the name largestByte. A name, such as largestByte, that's composed of a single identifier is called a simple name. Simple names are in contrast to qualified names, which a class uses to refer to a member variable that's in another object or class. This topic is covered further in the Using Objects section.

In the Java programming language, the following must hold true for a simple name:

• It must be a legal identifier. Recall from the preceding section that an identifier is an unlimited series of Unicode characters that begins with a letter.
• It must not be a keyword, a boolean literal (true or false), or the reserved word null.
• It must be unique within its scope. A variable can have the same name as a variable whose declaration appears in a different scope. In some situations, a variable can share names with another variable, which is declared in a nested scope. Scope is covered in the next section.

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By Convention:  Variable names begin with a lowercase letter and class names begin with an uppercase letter. If a variable name consists of more than one word, the words are joined together, and each word after the first begins with an uppercase letter (for example, isVisible). The underscore character ( _ ) is acceptable anywhere in a name, but by convention it is used only to separate words in constants (because constants are all caps by convention and thus cannot be case-delimited).

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