Control Statements in Java

We need to execute a set of statements based on a condition, we need to use control flow statements.

Types of control statements.

if statement
if-else statement
if-else-if statement
Nested if statement

1) if statement in Java

if statement is used to test the condition this statements get execute only when the given condition is true. If the condition is false then the statements inside if statement body are completely ignored.

Syntax:

if(condition){
//code to be executed
}

Example:

public class IfEx {
public static void main(String[] args) {
   int age=20;  
	 if(age>18) //checking condition // value change for false condition(age>22)
	 {
		System.out.print("Age is greater than 18");
	}
}
}

Show in Fig.

2) If-else statement in Java

if-else statement also tests the condition. when if condition is true then print your if body statement, else part statement do not tuch.

Otherwise if part statement is false then else block is executed.

Syntax:

if (condition) 
{
        statement-1
}
else
{
        statement-2
} 

Example1: Leap Year Program

public class LeapYearEx {    
public static void main(String[] args) {    
    int year=2024;    
    if(((year % 4 ==0) && (year % 100 !=0)) || (year % 400==0))  //Check if Condition True
    {  
        System.out.println("Leap Year");  
    }  
    else{  
        System.out.println("Not Leap Year");  
    }  
}    
}   

Example2: Odd and Even Program

public class IfElseExample {  
public static void main(String[] args) {  
   int number=13;  
     if(number%2==0)  //Check if the number is divisible by 2 or not , Condition False 
     {  
        System.out.println("even number");  
    }
    else
    {  
        System.out.println("odd number");  
    }  
}  
}  

Ternary Operator

Using Ternary Operator (? :) to perform the task like if...else statement. If the condition is true, the result of ? is returned. But, if the condition is false, the result of : is returned.

Example Ternary Operator :- Odd and Even Program

 
public class IfElseTernaryEx {    
public static void main(String[] args) {    
    int number=13;    
    //Using ternary operator  
    String output=(number%2==0)?"even number":"odd number";    
    System.out.println(output);  
}    
}    

3) if-else-if Statement

Multiple statements, executes one condition

Syntax

 
if(condition1){  
//code to be executed if condition1 is true  
}else if(condition2){  
//code to be executed if condition2 is true  
}  
else if(condition3){  
//code to be executed if condition3 is true  
}  
...  
else{  
//code to be executed if all the conditions are false  
}  

Example : Grading system for fail, D grade, C grade, B grade, A grade and A+

 
public class IfElseIfEx {  
public static void main(String[] args) {  
    int marks=60;  
      
    if(marks<50){  
        System.out.println("fail");  
    }  
    else if(marks>=50 && marks<60){  
        System.out.println("D grade");  
    }  
    else if(marks>=60 && marks<70){  
        System.out.println("C grade");  
    }  
    else if(marks>=70 && marks<80){  
        System.out.println("B grade");  
    }  
    else if(marks>=80 && marks<90){  
        System.out.println("A grade");  
    }else if(marks>=90 && marks<100){  
        System.out.println("A+ grade");  
    }else{  
        System.out.println("Invalid!");  
    }  
}  
}  

4) Nested if statement in Java

Nested if statement represents the if block within another if block. Here, the inner if block condition executes only when outer if block condition is true.

Syntax :

 
if(condition){    
     //code to be executed    
          if(condition){  
             //code to be executed    
    }    
}  

Example 1

 
public class NestedIfEx {    
public static void main(String[] args) {    
     
    int age=20;  
    int weight=80;    
    //Condition check on age and weight  
    if(age>=18){    
        if(weight>50){  
            System.out.println("You are eligible to donate blood");  
        }    
    }    
}} 
 

Output

Example 2 : Leap Year Program, Input by User

import java.util.Scanner;   
 
public class NestedifLeapyear
{
   public static void main(String[] args)
   {
      int year;     

       
      Scanner console = new Scanner(System.in);
      System.out.print("Enter a year : ");
      year = console.nextInt();

       if (year % 4 == 0)
      {
         if (year % 100 == 0)
         {
            if (year % 400 == 0)
            {
               System.out.println("A leap year");
            }
            else
            {
               System.out.println("Not a leap year");
            }
         }
         else
         {
            System.out.println("Print A leap year");
         }
      }
      else
      {
         System.out.println("Print Not a leap year");
      }
   }
}

Output

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