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Interesting facts about Increment and Decrement operators in Java

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  • Difficulty Level : Easy
  • Last Updated : 08 Jun, 2022

Increment operator is used to increment a value by 1. There are two varieties of increment operator: 

  • Post-Increment: Value is first used for computing the result and then incremented.
  • Pre-Increment: Value is incremented first and then the result is computed.

Example

Java




//INCREMENTAL OPERATOR
//Let's see what exactly happens when we use these operators with the help of a code.
 
import java.io.*;
 
class GFG {
    public static void main (String[] args) {
        //1. Post-Increment Operator
      int a = 5;
      int b = 7;
       
      int c = a++ + b; //Here 'a' will not incremented immediately, a++ will still return value 5.
      //  c = 5   + 7 and this will evaluate to 12.
       
      System.out.println("Post- Increment \n c = "+ c);
       
      //2. Pre-Increment Operator
       
      int A = 5;
      int B = 7;
       
      int C = ++A + B; //Here 'a' will be incremented immediately, and ++a will return value 6.
      //  C =  6  + 7   and this will evaluate to 13.
       
      System.out.println("Pre- Increment \n C = "+ C);
      
      //Example-
      int m = 1, n = 2;
       
      int o = m++ + n + ++m; // It goes like m++ = 1, n = 2, ++m = 1+ incremented 'm' from m++
      //                                                         = 1 + (1+m) = 1+ (1+1) = 3
      //  o = 1   + 2 +   3 = 6 
      System.out.println("Example \n o = "+ o);
    }
}


Decrement operator is used for decrementing the value by 1. There are two varieties of decrement operators. 

  • Post-decrement: Value is first used for computing the result and then decremented.
  • Pre-decrement: Value is decremented first and then the result is computed.

Example

Java




//DECREMETAL OPERATORS
//Let's see what exactly happens when we use these operators with the help of a code.
import java.io.*;
 
class GFG {
    public static void main (String[] args) {
         //1. Post-Decrement Operator
      int a = 5;
      int b = 7;
       
      int c = a-- + b; //Here 'a' will not decremented immediately, a-- will still return value 5.
      //  c = 5   + 7 and this will evaluate to 12.
       
      System.out.println("Post- Decrement \n c = "+ c);
       
      //2. Pre-Decrement Operator
       
      int A = 5;
      int B = 7;
       
      int C = --A + B; //Here 'a' will be decremented immediately, and --a will return value 4.
      //  C =  4  + 7   and this will evaluate to 11.
       
      System.out.println("Pre- Decrement \n C = "+ C);
      
      //Example-
      int m = 3, n = 2;
       
      int o = m-- + n + --m; // It goes like m-- = 3, n = 2, --m = (decremented 'm' from 'm--') - 1;
      //                                                         = (m -1) - 1 = (3 -1) -1 = 1
      //  o = 3   + 2 +   1 = 6 
      System.out.println("Example \n o = "+ o);
    }
}


Now let us do Interesting facts about Increment and Decrement operators:

  • Can only be applied to variables only
  • Nesting of both operators is not allowed
  • They are not operated over final variables
  • Increment and Decrement Operators can not be applied to boolean.

Let us discuss these 4 facts as listed above and do implement them as follows:

Fact 1: Can be applied to variables only

We can apply ++ and — operator only for variables but not for the constant values. If we are trying to apply ++ and — operator on the constant value then we will get a compile-time error which we will be seeing in example 1B after the below example as follows:

Example 1:

Java




// Java program to illustrate Increment
// and Decrement Operators
// Can be Applied to Variables Only
 
// Main class
public class GFG {
   
    // main driver method
    public static void main(String[] args)
    {
       
        int a = 10;
        int b = ++a;
        
       // Printing value inside variable
        System.out.println(b);
    }
}


Output

11

Example 2:

Java




// Java program to Illustrate Increment and Decrement
// operators Can be applied to variables only
 
// Main class
public class GFG {
 
    // main driver method
    public static void main(String[] args)
    {
        // Declaring and initializing variable
        int a = 10;
 
        int b = ++a;
 
        // This is change made in above program
        // which reflects error during compilation
        b = 10 ++;
 
        // Printing its value
        System.out.println(b);
    }
}


Output:

Fact 2: Nesting of both ++ and — operators are not allowed 

Example

Java




// Java program to Illustrate Nesting Can Not be Applied
// to Increment and Decrement Operators
 
// Main class
public class GFG {
 
    // Main driver method
    public static void main(String[] args)
    {
        int a = 10;
        int b = ++(++a);
 
        // Printing the value inside variable
        System.out.println(b);
    }
}


Output: 

Fact 3: Final variables can’t apply increment and decrement operator

The increment and decrement operators can not be applied to final variables because of the simple reason that their value can not be changed. 

Example

Java




// Java Program to Illustrate Increment and Decrement
// Operators Can not be applied to final variables
 
// Main class
public class GFG {
 
    // Main driver method
    public static void main(String[] args)
    {
        // Declaring and initializing final variable
        final int a = 10;
 
        int b = ++a;
 
        // Trying to print the updated value inside variable
        System.out.println(b);
    }
}


Output: 

Fact 4: Increment and Decrement Operators can not be applied to boolean

We can apply ++ and — operators for all primitive data types except Boolean type as it only has true and false which even sounds impractical.

Example

Java




// Java program to Illustrate Increment and Decrement
// Operators Can not be applied boolean data type
 
// Main class
public class GFG {
 
    // Main driver method
    public static void main(String[] args)
    {
        // Initially declaring boolean as false
        boolean b = false;
        b++;
 
        // Trying printing the bool value
        System.out.println(b);
    }
}


Output: 

This article is contributed by Bishal Kumar Dubey. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks. 

Please write comments if you find anything incorrect, or if you want to share more information about the topic discussed above.


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