Control Statements in Java

 

if statement

•         Use the if statement to specify a block of code to be executed if a condition is true.

 Syntax

 if (condition)

{
  // block of code to be executed if the condition is true
  }

Example

class sample

{

         public static void main(String args[])

         {

                 int a=10, b=20;

                 if(a>b)

                   System.out.println(“A is greater than B”);

         }

}

package Conditonal_Statements;

public class Simple_if {

// Java program to illustrate If statement

public static void main(String args[])

{

int i = 10;

if (i < 15)

{System.out.println("10 is less than 15");}

}

}

If… else statement

•         Use the if statement to specify a block of code to be executed if a condition is true.

•         Use the else statement to specify a block of code to be executed if the condition is false.

Syntax

if (condition)

 {
  // block of code to be executed if the condition is true
} 

else 

{
  // block of code to be executed if the condition is false
}

Example – if…else

int a = 20;
if (a <18)

 {
  System.out.println("Good day.“);
} 

else

 {
  System.out.println("Good evening.“);
}

Output:

Good evening

package Conditonal_Statements;

import java.util.Scanner;

public class if_else {

public static void main(String args[]) {

int year;

System.out.println("Enter Year : ");

Scanner in = new Scanner(System.in);

year = in.nextInt();

if (year % 4 == 0 || (year % 100 == 0 && year % 400 == 0)) {

System.out.println("Year " + year + " is a leap year");

} else {

System.out.println("Year " + year + " is not a leap year");

}

}

}

If… else if statement

•         Use the else if statement to specify a new condition if the first condition is false.

Syntax

if (condition1)

 {
  // block of code to be executed if condition1 is true
} 

else if (condition2)

{
  // block of code to be executed if the condition1 is false and condition2 is true
} 

else 

{
  // block of code to be executed if the condition1 is false and condition2 is false
}

 

Example

int a = 22;
if (a < 10)

 {
  System.out.println( "Good morning.“);
}

 else if (a < 20)

{
 System.out.println( "Good day.“);
} 

else

 {
  System.out.println( "Good evening.“);
}

Output

Good Evening

package Conditonal_Statements;

import java.util.Scanner;

public class Nested_if {

public static void main(String args[])

{

/*

Nested if Statement

A company insures its drivers in the following cases:

a. If the driver is married.

b. If the driver is unmarried, male & above 30 years of age.

c. If the driver is unmarried, female & above 25 years of age.

*/

Scanner in =new Scanner(System.in);

System.out.println("Enter The Marital Status M/U: ");

char marital=in.next().charAt(0);

if(marital=='u' || marital=='U' )

{

System.out.println("Enter The Gender M/F: ");

char gender=in.next().charAt(0);

System.out.println("Enter The Age : ");

int age=in.nextInt();

if((gender=='M'||gender=='m')&& age>=30)

{

System.out.println("You are Eligible for Insurance");

}

else if((gender=='F'||gender=='f')&& age>=25)

{

System.out.println("You are Eligible for Insurance");

}

else

{

System.out.println("You are Not Eligible for Insurance");

}

}

else if(marital=='m' || marital=='M' )

{

System.out.println("You are Eligible for Insurance");

}

else {

System.out.println("Invalid Input");

}

}

}

Switch Statement

Use the switch statement to select one of many code blocks to be executed.

Syntax:

switch(expression)

 {
  case x:
    // code block
    break;
  case y:
    // code block
    break;
  default:
    // code block

}

This is how it works:

•        The switch expression is evaluated once

•        The value of the expression is compared with the values of each case

•        If there is a match, the associated block of code is executed

Example:

int day = 4;
switch (day) {
  case 1:
    System.out.println( "Monday“);
    break;
  case 2:
    System.out.println("Tuesday“);
    break;
  case 3:
    System.out.println( "Wednesday“);
    break;
  case 4:
    System.out.println( "Thursday“);
    break;
  case 5:
   System.out.println( "Friday“);
    break;
  case 6:
    System.out.println( "Saturday“);
    break;
  case 7:
    System.out.println( "Sunday“);
    break;

default:

      System.out.println(“Invalid Day”);
}

Output: Thursday

package Conditonal_Statements;

import java.util.Scanner;

//Switch Case Statement in Java

public class switch_demo {

public static void main(String args[]) {

int a,b,c,ch;

System.out.println("1.Addition");

System.out.println("2.Subtraction");

System.out.println("3.Multiplication");

System.out.println("4.Division");

System.out.println("Enter Your Choice : ");

Scanner in =new Scanner(System.in);

ch=in.nextInt();

System.out.println("Enter 2 Nos : ");

a=in.nextInt();

b=in.nextInt();

switch (ch)

{

case 1:

c=a+b;

System.out.println("Addition : " +c);

break;

case 2:

c=a-b;

System.out.println("Subtraction : "+c);

break;

case 3:

c=a*b;

System.out.println("Multiplication : "+c);

break;

case 4:

c=a/b;

System.out.println("Division : "+c);

break;

default:

System.out.println("Invalid Selection");

break;

}

}

}