A local variable in Java is a variable that’s declared within the body of a method. Then you can use the variable only within that method. Other methods in the class aren’t even aware that the variable exists.
Here’s a program that uses a local variable:
public class HelloApp
{
public static void main(String[] args)
{
String helloMessage;
helloMessage = "Hello, World!";
System.out.println(helloMessage);
}
}
You don’t specify static on a declaration for a local variable. If you do, the compiler generates an error message and refuses to compile your program.
Unlike class and instance variables, a local variable is fussy about where you position the declaration for it: You must place the declaration before the first statement that actually uses the variable.
You may also declare local variables within blocks of code marked by braces. For example:
if (taxRate > 0)
{
double taxAmount;
taxAmount = subTotal * taxRate;
total = subTotal + total;
}
Local variables are not given initial default values. Thus, you must assign a value before you use a local variable.
One way to initialize a variable is to code an assignment statement following the variable declaration. Assignment statements have this general form:
variable = expression;
Here, the expression can be any Java expression that yields a value of the same type as the variable. For example, here’s a method that declares a local variable named i, and then initializes the variable before using it:
public static void main(String[] args)
{
int i;
i = 0;
System.out.println("i is " + i);
}
Another way to initialize a variable is to use an initializer, which lets you assign an initial value to a variable at the time you declare the variable. Here’s the general form:
type name = expression;
Here are some examples:
int x = 0;
String lastName = "Lowe";
double radius = 15.4;
In each case, the variable is declared and initialized in a single statement.
When you declare more than one variable in a single statement, each variable can have its own initializer:
int x = 5, y = 10;
When you declare two class or instance variables in a single statement but use only one initializer, the initializer applies only to the last variable in the list. For example:
static int x, y = 5;
Here, only y is initialized.
Here’s a program that uses a local variable:
public class HelloApp
{
public static void main(String[] args)
{
String helloMessage;
helloMessage = "Hello, World!";
System.out.println(helloMessage);
}
}
You don’t specify static on a declaration for a local variable. If you do, the compiler generates an error message and refuses to compile your program.
Unlike class and instance variables, a local variable is fussy about where you position the declaration for it: You must place the declaration before the first statement that actually uses the variable.
You may also declare local variables within blocks of code marked by braces. For example:
if (taxRate > 0)
{
double taxAmount;
taxAmount = subTotal * taxRate;
total = subTotal + total;
}
Local variables are not given initial default values. Thus, you must assign a value before you use a local variable.
One way to initialize a variable is to code an assignment statement following the variable declaration. Assignment statements have this general form:
variable = expression;
Here, the expression can be any Java expression that yields a value of the same type as the variable. For example, here’s a method that declares a local variable named i, and then initializes the variable before using it:
public static void main(String[] args)
{
int i;
i = 0;
System.out.println("i is " + i);
}
Another way to initialize a variable is to use an initializer, which lets you assign an initial value to a variable at the time you declare the variable. Here’s the general form:
type name = expression;
Here are some examples:
int x = 0;
String lastName = "Lowe";
double radius = 15.4;
In each case, the variable is declared and initialized in a single statement.
When you declare more than one variable in a single statement, each variable can have its own initializer:
int x = 5, y = 10;
When you declare two class or instance variables in a single statement but use only one initializer, the initializer applies only to the last variable in the list. For example:
static int x, y = 5;
Here, only y is initialized.
