Instance Variables vs Local Variables in JAVA

Instance Variables:-

• Variables that are declared in the global scope i.e. at class level.

• By default, their values are initialized to default values depending on data types. For ex. for int data type, value is initialized to 0.

• The memory for instance variables is allocated on heap at the time of object creation.

•     public class Laptop {
          int ram;
          String brand;
          public void display() {
              System.out.println(brand+" laptop is having ram of "+ram+"gb");
          }
      }
  

Local Variables:-

• Variables that are declared in the local scope i.e. at block level or method level or in the loops or conditional statements.

• By default, their values are not initialized as instance variables. Hence their values needs to be initialized everytime we declare a local variable

• The memory for instance variables is allocated at stack level.

•     public class LocalVariable {
          public void doSomething() {
              int i = 10; 
      // this variable is declared inside method block and it has scope inside method only
              System.out.println(i);
          }
      }