Page 333 - Computer_Science_F5

Computer Science (b) Types of Variable
There are three types of variables in java: local variable, instance variable and static
variable.

(i) Local variable
FOR ONLINE READING ONLY
Local variables are declared inside the methods, constructors, or blocks. It is usually
created when the method, constructor or block start to be executed. It is destroyed once
the method, constructor, or block finishes execution. Local variables are visible only
within the declared method, constructor, or block. They are implemented internally
at stack level. There is no default value for local variables, so local variables should
be declared and an initial value should be assigned before the first use. In this case,
access specifiers cannot be used for local variables. Program Example 5.1 shows the
local variable program:

Program Example 5.1:

Java program to demonstrate local variable

public class Car {
public static void main(String[] args) {
// Local variable
int numOfDoors = 5; // This variable only exists within this method
System.out.println(“My father bought a car with “ + numOfDoors + “ doors.”);
}
}

variables can also be declared at the
(ii) Instance variable class level. Access modifiers in Java,
This refers to a variable declared within such as Default, Private, Protected,
a class but outside any method. They are and Public, restrict the scope of these
declared in a class, not inside a method, variables, methods, and constructors.
constructor, or block. When an object is By default, instance variables are visible
allocated in the heap, a storage space is to all methods, constructors, and blocks
created for each instance variable. These within the class. It is recommended to
variables hold values that are needed make these variables private, but they
by multiple methods, constructors, can be made visible to subclasses using
or blocks, or they represent essential access modifiers. Instance variables
parts of an object’s state that should be have default values:
accessible throughout the class. Instance (1) Numbers, the default value is 0,

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for Advanced Secondary Schools

Computer Science Form 5.indd 324 23/07/2024 12:34