else if condition and Nested if else in Java

Sometime as a programmer you want to use a set of conditions where in you want that if your first condition is false then only move to check the next condition, and if that is also false then only move to check the next condition and so on. To address such scenarios java provides if then else if statement. You can specify another condition with else if statement which is evaluated only when it's prior if or else if condition is false.

if else if condition returns true, the else if block will be executed, if it returns false, computer will move to next else if statement and evaluates the condition expression. This process goes on until any of the expression returns true or all the else if statements are finished. Once any of the expression returns true, code inside that conditional statement is executed and all other condition statements after that are not executed. If all conditional statements returns false, then final else block(if any) will be executed. The syntax of if-then-else if statement is:

 if(condition)
   {
    // code to be executed inside if block
   }
 else if(condition-1)
   {
     // code to be executed inside this else if block
   } 
 else if(condition-2)
   {
     // code to be executed inside this else if block
   } 
   .
   .
   .
 else if(condition-N)
   {
     // code to be executed inside this else if block
   } 
 else
   {
     // code to be executed inside else block
   }

This is also called as else if ladder which is mostly used when programmer wants to select one block of code among many.

Can I use else if statement without if statement ?

No, you can not use else if statement without if statement.

Control flow diagram of if-else if Statement

if else if program in Java

 public class IfElseIfStatement
   {
     public static void main(String [] args)
        {          
           int num1 = 20, num2 = 20; 
           if(num1 > num2)
            {
              System.out.println("num1 is greater than num2");
            }
            else if(num1 == num2)
            {
              System.out.println("num1 is equal to num2");
            } 
            else
            {
              System.out.println("num1 is less than num2");
            } 
            System.out.println("code to be executed after else if ladder");                   
         }
   }

Output:

num1 is equal to num2
code to be executed after else if ladder

Nested if-else Statement in Java

Java allows programmer to place if else block inside another if or else block. This is called as nested if else statement. Programmer can do any level of nesting in program which means you can place if else block inside another if or else block up to any number of times. Inner if block is executed only when outer if condition is true.

 if(condition-1)
   {
     // code to be executed inside first if block
     if(condition-2)
       {
         // code to be executed inside second if block
         if(condition-3)
           {
             // code to be executed inside third if block
             . . . . .
             . . . . .
           }
         else
           {
             // code to be executed inside else block
           }
         // code to be executed inside second if block
       } 
     // code to be executed inside first if block   
   }
 else
   {
     if(condition-4)
       {
         // code to be executed inside this if block
       }
   }

Nested if else program in Java

 public class IfElseStatement
   {
     public static void main(String [] args)
        {          
           int num1 = 20; 
           if(num1 >= 10)
             {
                if(num1<100)
                  {
                    System.out.println("num1 is a double digit number");
                  }
                else
                  {
                    System.out.println("num1 is not a double digit number");
                  }
              }
            else
             {
               System.out.println("num1 is less than 10");
             }  
            System.out.println("code after nested if else block");                   
         }
   }

Output:

num1 is a double digit number
code after nested if else block

★★★

Ensure there is space between else if, it should not be elseif.
Final else block in else if ladder is optional, it's programmer's choice whether to use or not.
else if is also part of conditional or decision making statements.
If no curly brackets {} is used with else if keyword, only first line of code after else if keyword will be considered as part of else if statement.

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