Scope of local variables

The scope of a variable is the region of a program in which the variable is visible, i.e., in which it is accessible by its name and can be used.

In Java, the scope of a local variable is the body of the method in which it is declared. In other words, the variable is visible in the body of the method where its declaration appears, but it is not visible on the outside the method.

Clearly, as we have already said in Unit 2, a variable cannot be used in the body of a method before it has been declared.

Notes:

• In fact, a more general scope rule holds: the scope of a local variable extends from the point of its declaration to the end of the block that encloses it. A block is a statement of the form {...} (see later). Hence, a local variable is visible in the block in which it is declared (including sub-blocks, if present), but is not visible outside that block.
• In Java, the scope of a variable is a completely static notion. Indeed, it can be determined by analyzing the structure of the program, without considering its execution. Most current programming languages support such a notion of static scope.
• If follows that the notion of scope is relevant at compile time.