Java if???else Statement

The if-else statement is used to execute the block of codes, if the specified condition is satisfied.

if Statement

Syntax for if statement

if(condition){
   // block of codes.
}

Here, the if statement takes a condition and if the condition is satisfied, then it will execute the block of codes.

Example for if statement

class Main {
  public static void main(String[] args) {

    int age = 19;

    // checks if number is less than 0
    if (age >= 18) {
      System.out.println("Welcome");
    }

    System.out.println("End");
  }
}

Output

 Welcome
 End

In the above program, the value of age variable is 17. The if statement checks whether age is greater than or equal to 18.

If the condition is true, the block of code inside it will execute; if not, it is skipped.

if-else Statement

The if-else statement is used to execute the if block statement(s); if the condition is satisfied. If the condition is not satisfied, then it will execute the else block statement(s).

Syntax for if-else statement

if(condition){
  // block of codes
 }
 else {
 // block of codes
 }

Example program for if-else statement

class Main {
  public static void main(String[] args) {

    int a = 100,b=200;

    // checks if number is less than 0
    if (a>b) {
      System.out.println(a +" is greater than "+ b);
    }
    else{
        System.out.println(b +" is greater than "+ a);
    }
  }
}

Output

200 is greater than 100

In the above program, we have checked whether the value of a is greater that the value of b.

The variable a has the value 100 and b has the value as 200.Here, the condition is not true, so the else block is executed.

else if Statement

If you want to check multiple condition, then we have to use else-if statement.

Syntax for else-if statement

if (condition1) {
  // block of codes
} else if (condition2) {
  // block of codes
} else {
  // block of codes
}

Here the if block condition is checked first. If the condition is not satisfied, then it checks the condition in else-if statement. If that condition is satisfied, then else-if block is executed.

If both the condition is not satisfied, then the else block is executed.

Example program for else-if statement

class Main {
  public static void main(String[] args) {

    int a = 100,b=200, c=300;

    // checks if number is less than 0
    if (a >b && a>c) {
      System.out.println(a +" is the biggest number.");
    }
    else if(b>c){
        System.out.println(b +" is the biggest number.");
    } 
    else{
        System.out.println(c +" is the biggest number.");
    }
  }
}

Output

300 is the biggest number.

Here, in the if statement we check whether the value of a is greater than b and c. If it is satisfied, then the if block is executed.

If the above condition is not satisfied, then with else-if statement we wil check whether b is greater than c. If it is satisfied, then else-if block is executed.

If both the conditions are not satisfied, then else block is executed.

Nested if???else Statement

In java, it is possible to nest if-else statement inside an other if-else statement.

Syntax for nested if statements

//check if the first condition holds
if (condition 1) {
    
    //if the second condition holds
    if (condition 2) {
        do something
    }
    //if the second condition does not hold
    else {
        do something else
    }
    
}
// if the first condition does not hold
else{
    
    //if the third condition holds
    if (condition 3) {
        do something
    }
    //if the third condition does not hold
    else {
        do something else
    }
    
}

In the above syntax, we have the if-else statement inside the if block as well as else block.

Let us see a program to get a number from the user and check whether the number is even and divisible by 4 or the number is odd and divisible by 3.

Example for nested if statement

import java.util.*;

class Main {
  public static void main(String[] args) {
  // variable to store the given number
  int n;
  
  Scanner scanner = new Scanner(System.in);
  //take input from the user
  n= scanner.nextInt();

  //if else condition to check whether the number is even or odd
  if (n % 2 == 0) {

    //the number is even
    System.out.print("Even Number");

    //nested if else condition to check if n is divisible by 4 or not
    if (n % 4 == 0) {
      //the number is divisible by 4
      System.out.print("and divisible by 4");
    } else {
      //the number is not divisible by 4
      System.out.print("and not divisible by 4");
    }
  } else {
    //the number is odd
    System.out.print("Odd Number");

    //nested if else condition to check if n is divisible by 3 or not
    if (n % 3 == 0) {
      //the number is divisible by 3
      System.out.print("and divisible by 3");
    } else {
      //the number is not divisible by 3
      System.out.print("and not divisible by 3");
    }

  }
}
}

Output

10
Even Numberand not divisible by 4