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Conditional Statements in Java
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| Java - Conditional Statements |
Conditional statements allow us to control the flow of execution based on specific conditions. In this guide, we will explore key concepts such as if, else, else if, and nested conditions.
1. If...Else Statement
The if...else statement executes a block of code when a specified condition is met; otherwise, the else block runs.
Example:
A vending machine dispenses items based on token input.
class VendingMachine {
public static void main(String[] args) {
int token = 20;
if (token == 20) {
System.out.println("Collect Water Bottle");
} else {
System.out.println("Invalid Token");
}
}
}
If the token is not 20, the message "Invalid Token" is displayed.
2. Else If Statement :
The else if statement allows multiple conditions to be checked sequentially. If no conditions are met, the else block executes.
Example:
The vending machine now supports multiple items.
class VendingMachine {
public static void main(String[] args) {
int token = 30;
if (token == 10) {
System.out.println("Collect Chips");
} else if (token == 20) {
System.out.println("Collect Water Bottle");
} else if (token == 30) {
System.out.println("Collect Soft Drink");
} else {
System.out.println("Invalid Token");
}
}
}
true.3. Nested Conditions
Conditional statements can be nested within each other to handle complex logic.
Example:
Selecting a soft drink based on token input.
class VendingMachine {
public static void main(String[] args) {
int token = 30;
char softDrink = 'S';
if (token == 30) {
if (softDrink == 'S') {
System.out.println("Collect Sprite");
} else if (softDrink == 'F') {
System.out.println("Collect Fanta");
} else {
System.out.println("Invalid Option");
}
} else {
System.out.println("Invalid Token");
}
}
}
Here, if the token is valid, a second condition determines the specific drink.
4. Optional Else Statement
The else block is optional; if omitted, nothing executes when conditions are unmet.
Example:
class VendingMachine {
public static void main(String[] args) {
int token = 30;
char softDrink = 'S';
if (token == 30) {
if (softDrink == 'S') {
System.out.println("Collect Sprite");
} else if (softDrink == 'F') {
System.out.println("Collect Fanta");
}
}
}
}
Without an else block, no message appears if conditions are unmet.
5. Common Mistakes :
Misplacing Else Statement :
The else statement must follow an if block without interruptions.
Incorrect:
if (false) {
System.out.println("If Block");
}
System.out.println("After If");
else { // ❌ Error: 'else' without 'if'
System.out.println("Else Block");
}
Correct :
if (false) {
System.out.println("If Block");
} else {
System.out.println("Else Block");
}
System.out.println("After Else");
Output :
Else Block
After Else
Incorrect Else If Order :
The else if block must come before the else block.
Incorrect:
if (token == 10) {
System.out.println("Collect Chips");
} else if (token == 20) {
System.out.println("Collect Water Bottle");
} else {
System.out.println("Invalid Token");
} else if (token == 30) { // ❌ Error
System.out.println("Collect Soft Drink");
}
Correct :
if (token == 10) {
System.out.println("Collect Chips");
} else if (token == 20) {
System.out.println("Collect Water Bottle");
} else if (token == 30) {
System.out.println("Collect Soft Drink");
} else {
System.out.println("Invalid Token");
}
Output:
Collect Water Bottle
6. If...Else Without Curly Braces
Curly braces {} can be omitted when the block contains only one statement.
Example:
class VendingMachine {
public static void main(String[] args) {
int token = 20;
if (token == 20) System.out.println("Collect Water Bottle");
else System.out.println("Invalid Token");
}
}
Summary
- The
if...elsestatement executes code based on a condition. - The
else ifstatement allows multiple conditions. - Nested conditions handle complex scenarios.
- The
elsestatement is optional. - The order of
if,else if, andelsemust be correct. - Curly braces can be omitted for single-statement blocks.
By mastering these concepts, you can effectively control program flow in Java applications.
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