What is local variable and instance variable in Java?

What is local variable and instance variable in Java?

In Java, a local variable and an instance variable are two types of variables that have different scopes and lifetimes.

Local Variables

A local variable is a variable that is declared within a method or a block of code. Its scope is limited to the block where it is declared, and its lifetime is the duration of the execution of that block. Local variables are created when the method is called and destroyed when the method returns. They are not stored in memory after the method finishes executing.

Local variables are declared using the int, double, boolean, or other primitive types, or with reference types such as String. Here's an example:

public void myMethod() {
int x = 5; // local variable x
System.out.println(x);
}

In this example, x is a local variable that is declared within the myMethod() method. It has no relationship to any instance variables or global variables.

Instance Variables

An instance variable, also known as an attribute or field, is a variable that is associated with an object (instance) of a class. Each object has its own copy of the instance variable, and changes made to one object's instance variable do not affect other objects. Instance variables are created when an object is instantiated, and they exist until the object is garbage-collected.

Instance variables are declared using the private, protected, or public access modifiers within a class. Here's an example:

public class MyClass {
private int x = 5; // instance variable x
public void myMethod() {
System.out.println(x);
}
}

In this example, x is an instance variable that is associated with the MyClass object. Each object of type MyClass has its own copy of the x variable.

Key Differences

Here are the key differences between local variables and instance variables:

In summary, local variables are used to store temporary values within a specific scope, whereas instance variables are used to store attributes that describe an object and persist throughout its lifetime.

Types of variables in java with examples w3schools

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