Instance Variable in Java Programming

Java Programming Language Variables in java (Article) Variables in java (Program)

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Program:

 class InstanceVariable {
int data=50;//instance variable

public static void main(String []args) {
      /* In this example if you want to access instanec variable'data' then you 
      have to create an instane of InstancVariable class like this*/
      InstanceVariable iv = new InstanceVariable();
      /* here iv is the name of the object or instance of the
	   InstanceVariable class */
      System.out.println(iv.data);
      /* to access the instance variable 'data' you have to write iv.data

   }
}

Output:

50
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Explanation:

Rules for Instance variable in Java

  • Instance variables can use any of the four access levels
  • They can be marked final
  • They can be marked transient
  • They cannot be marked abstract
  • They cannot be marked synchronized
  • They cannot be marked strictfp
  • They cannot be marked native
  • They cannot be marked static

Cheatsheet

  • Public, Private, Protected all 3 access modifiers can be applied to Instance Variable(Default also).
  • Instance variable will get default value means instance variable can be used without initializing it. Same is not true for Local Variable.
  • Instance Variable can be marked final.
  • Instance Variable can be marked transient.
  • Instance Variable cannot be abstract.
  • Instance Variable can not have synchronized modifier.
  • Instance Variable can not have strictfp modifier.
  • Instance Variable can not have the native modifier.
  • Instance Variable can not have Static modifier as it will become Class level variable.
INSTANCE VARIABLE TYPE DEFAULT VALUE
boolean false
byte (byte)0
short (short) 0
int 0
long 0L
char u0000
float 0.0f
double 0.0d
Object null

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