Java Decision Statement

Decision Statement or selection statement allow you to take a decision as which statement will to be executed next. It select one block of statements out of many blocks. Decision statement includes: if, nested if, and switch.

1. If - Specifies the condition and execute the statements only if the condition is true, and if the condition is false, statements will not be executed.

if (condition)
{
    statement 1;
    statement 2;
    .
    .
    statement n;
}

Example 1: Check it is eligible for vote or not.

package ifstatement;
public class Ifstatement {
    public static void main(String[] args) {
        int n=20;
        if(n>=18)
            System.out.println("User is eligible for vote");
    }    
}

2. if–else condition: if else condition is divided into 2 parts. First part statements will execute if the condition is true and if the condition is false other part of the statements will execute. Both parts of statements will not be executed in either condition. Syntax:

if (condition)
{
    statement 1;
    statement 2;
      .
      .
    statement n;
}	
else
{
    statement 1;
    statement 2;
      .
      .
    statement n;
}

Example 2: Re-write the above program using if-else condition.

package ifstatement;
public class Ifstatement {
    public static void main(String[] args) {
    int n=15;
    if(n>=18)
        System.out.println("User is eligible for vote");
    else
        System.out.println("User is not eligible for vote");
    }    
}

3. Nested if - It is useful when multiple conditions are to be applied.

if (condition 1)
{
    statement 1;
}
else 
    if (condition 2)
    {
        statement 2;
    }
    else
    {
        statement 3;
    }

In the above example, if condition 1 is true first block of statements will be executed, rest of the condition will not executed nor checked. If condition 1 is false and condition 2 is true, than 2nd block of Statements will be executed. If the condition 1 and condition 2 is false than 3rd block of statements will execute.

Example 3: Find greater number from 3 numbers.

package ifstatement;
public class Ifstatement {
    public static void main(String[] args) {
        int a=10, b=25, c=20;
        if(a>b && a>c)
            System.out.println("A is greater");
        else
        if(b>a && b>c)
            System.out.println("B is greater");
        else
            System.out.println("C is greater");
    }
}

Example 4: Input 3 numbers and find greater number.

package ifstatement;
import java.util.Scanner;
public class Ifstatement {
    public static void main(String[] args) {
        int a, b, c;
        Scanner scan = new Scanner(System.in);
        System.out.println("Enter 3 numbers: ");
        a = scan.nextInt();
        b = scan.nextInt();
        c = scan.nextInt();
        
        if(a>b && a>c)
            System.out.println("A is greater");
        else
        if(b>a && b>c)
            System.out.println("B is greater");
        else
            System.out.println("C is greater");
    }    
}