Java Control Statements - JAVA DEVELOPMENT Training By Om Sir

Java Conditions and If Statements

Java supports the usual logical conditions from mathematics:

Less than: a < b
Less than or equal to: a <= b
Greater than: a > b
Greater than or equal to: a >= b
Equal to a == b
Not Equal to: a != b

You can use these conditions to perform different actions for different decisions.

Java has the following conditional statements:

Use if to specify a block of code to be executed, if a specified condition is true
Use else to specify a block of code to be executed, if the same condition is false
Use else if to specify a new condition to test, if the first condition is false
Use switch to specify many alternative blocks of code to be executed

The if Statement

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

if (condition) {

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

}

Example :-

public class Main {

public static void main(String[] args) {

if (20 > 18) {

System.out.println("20 is greater than 18"); // obviously

}

We can also test variables:

public class Main {

public static void main(String[] args) {

int x = 20;

int y = 18;

if (x > y) {

System.out.println("x is greater than y");

}

The else Statement

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 :-

public class Main {

public static void main(String[] args) {

int time = 20;

if (time < 18) {

System.out.println("Good day.");

} else {

System.out.println("Good evening.");

}

The 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 :-

public class Main {

public static void main(String[] args) {

int time = 22;

if (time < 10) {

System.out.println("Good morning.");

} else if (time < 20) {

System.out.println("Good day.");

} else {

System.out.println("Good evening.");

}

Java Switch Statements

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.
The break and default keywords are optional.

Example :-

public class Main

{

public static void main(String[] args)

{

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("Looking forward to the Weekend");

}