throw and throws in Java

These are two related but distinct concepts in Java's exception handling mechanism.

`throw` keyword

Used to explicitly throw an exception from a method or block of code
You can throw either checked or unchecked exceptions
Syntax: throw new ExceptionType("message");

Example:

public void checkAge(int age) {
    if (age < 18) {
        throw new ArithmeticException("Access denied - You must be at least 18 years old.");
    }
    System.out.println("Access granted");
}

`throws` keyword

Used in method signature to declare that a method might throw one or more exceptions
Primarily used for checked exceptions (though you can use it for unchecked exceptions too)
Caller of the method must handle or declare these exceptions
Syntax: returnType methodName() throws Exception1, Exception2 {...}

Example:

public void readFile() throws FileNotFoundException, IOException {
    // code that might throw these exceptions
}

Key Differences

Feature	`throw`	`throws`
Purpose	To explicitly throw an exception	To declare possible exceptions
Location	Inside method body	In method signature
Exceptions	Can throw one exception at a time	Can declare multiple exceptions
Type	Statement	Clause

Combined Example

public class Example {
    // Method declares it might throw IOException
    public void processFile(String filePath) throws IOException {
        if (filePath == null) {
            // Explicitly throwing an exception
            throw new IllegalArgumentException("File path cannot be null");
        }

        // Code that might throw IOException
        FileReader file = new FileReader(filePath);
        // ... more code
    }
}