Variables

Published May 6, 2021Updated Jan 12, 2024
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Variables are used whenever there’s a need to store a piece of data. A variable contains data that can be used in the program elsewhere. Using variables also ensures code re-usability since it can be used to replace the same value in multiple places.

Declaring a Variable

To declare a variable in Java, any of these three keywords can be used along with a variable name:

  • The data type.
  • The variable name.
  • The value.
int age = 28;
char grade = 'A';
boolean late = true;
byte b = 20;
long num1 = 1234567;
short no = 10;
float k = (float)12.5;
double pi = 3.14;

The equal sign = is used to assign a value to a variable. After the initial assignment is made, the value of a variable can be updated to new values as needed.

Types of Variables

In Java, there are three types of variables that can be used and each of them serves a different purpose. These types are discussed below one-by-one.

1. Local Variables

Local variables are the ones that are declared within a method or a block of code and are only accessible within that scope:

void exampleMethod() {
int localVar = 5;
// localVar is only available within .exampleMethod()
}

2. Instance Variables

Instance variables are the ones that are declared within a class but outside the scope of a method. Each instance of the class includes a unique version of the variable:

public class MyClass {
int instanceVar = 10;
// Each instance of MyClass has its own instanceVar
}

3. Static Variables

Static variables are the ones that belong to a class rather than its instances. In the case of these variables, only one copy is created in a class and distributed among all instances of that particular class:

public class SharedClass {
static int staticVar = 100;
// All instances of SharedClass share the same staticVar
}

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