Scoping
Most procedural languages have the concept of scope. This determines both the visibility and lifetime of the names defined within that scope. In C, C++, and Java, scope is determined by the placement of curly braces {}. So for example:
{
int x = 12;
// Only x available
{
int q = 96;
// Both x & q available
}
// Only x available
// q “out of scope”
}
A variable defined within a scope is available only to the end of that scope.
Any text after a ‘//’ to the end of a line is a comment.
Indentation makes Java code easier to read. Since Java is a free-form language, the extra spaces, tabs, and carriage returns do not affect the resulting program.
Note that you cannot do the following, even though it is legal in C and C++:
{
int x = 12;
{
int x = 96; // Illegal
}
}
The compiler will announce that the variable x has already been defined. Thus the C and C++ ability to “hide” a variable in a larger scope is not allowed, because the Java designers thought that it led to confusing programs.
