Throw keyword in Java - Mini Project: Build & Apply

Using the Throw Keyword in Java

📖 Scenario: You are creating a simple banking application. You want to make sure that users cannot withdraw more money than they have in their account.

🎯 Goal: Build a Java program that uses the throw keyword to stop the program and show an error message if a user tries to withdraw too much money.

📋 What You'll Learn

Create a variable to hold the current account balance.

Create a variable to hold the amount to withdraw.

Use the throw keyword to raise an exception if the withdrawal amount is greater than the balance.

Print a message showing the remaining balance if the withdrawal is allowed.

💡 Why This Matters

🌍 Real World

Banking apps and many other programs use exceptions to stop errors and keep data safe.

💼 Career

Knowing how to use <code>throw</code> helps you write safer Java programs that handle mistakes properly.

1

Set up account balance and withdrawal amount

Create a variable called balance and set it to 500. Create another variable called withdrawAmount and set it to 600.

Java

int balance = 0;
int withdrawAmount = 0;
// Your code here

Need a hint?

Use int to create whole number variables.

2

Prepare to check withdrawal

Create a variable called errorMessage and set it to the string "Insufficient funds".

Java

int balance = 500;
int withdrawAmount = 600;
String errorMessage = "";
// Your code here

Need a hint?

Use String to store text messages.

3

Use throw to stop withdrawal if funds are low

Write an if statement that checks if withdrawAmount is greater than balance. Inside the if, use throw new IllegalArgumentException(errorMessage); to stop the program with the error message.

Java

int balance = 500;
int withdrawAmount = 600;
String errorMessage = "Insufficient funds";

// Your code here

Need a hint?

The throw keyword is used to raise an exception and stop the program.

4

Show remaining balance if withdrawal allowed

Write a System.out.println statement that prints "Remaining balance: " plus the result of balance - withdrawAmount.

Java

int balance = 500;
int withdrawAmount = 600;
String errorMessage = "Insufficient funds";

if (withdrawAmount > balance) {
    throw new IllegalArgumentException(errorMessage);
}

// Your code here

Need a hint?

If the withdrawal is too big, the program will stop and show the error message.