difference between throw, throws, and Throwable

Here's a clear and simple difference between throw, throws, and Throwable in Java, with explanations and examples:

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🔁 Comparison Table

Keyword	Description	Use Case	Example Code
throw	Used to manually throw an exception object	Inside method body	throw new ArithmeticException();
throws	Declares that a method may throw exceptions (checked/unchecked)	In method signature	public void read() throws IOException
Throwable	Superclass of all exceptions and errors	For catching or creating custom exceptions	Throwable t = new Exception();

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🔹 1. throw – used to actually throw an exception

public class Example {
    public static void main(String[] args) {
        throw new ArithmeticException("Divide by zero");
    }
}

• 💡 Used inside methods
• Only one exception object can be thrown at a time

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🔹 2. throws – used to declare potential exceptions

public void readFile() throws IOException {
    FileReader fr = new FileReader("abc.txt");  // may cause checked exception
}

• 💡 Used in method declaration
• Can declare multiple exceptions

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🔹 3. Throwable – parent class of all exceptions and errors

public class Test {
    public static void main(String[] args) {
        try {
            throw new Exception("Test");
        } catch (Throwable t) {  // catches Exception and Error
            System.out.println("Caught: " + t);
        }
    }
}

• 💡 Can catch any throwable (exceptions or errors)
• Rarely used directly, but helpful in logging/final catch block

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🧠 Summary:

Term	Meaning	Type
throw	Actually throws exception	Statement
throws	Declares possible exceptions	Keyword
Throwable	Base class of all errors & exceptions	Class

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Here are 7 commonly asked interview questions on throw, throws, and Throwable with concise answers:

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✅ 1. What is the difference between throw and throws in Java?

Answer:

throw is used within a method to explicitly throw an exception.

throws is used in the method declaration to declare which exceptions can be thrown.

> Example:

throw new ArithmeticException();

public void read() throws IOException {}

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✅ 2. Can we throw multiple exceptions using a single throw statement?

Answer:

No. throw can only throw one exception at a time.

throw new IOException(); // ✅ Only one exception

✅ 3. Can a method have multiple exceptions in the throws clause?

Answer:

Yes. Multiple exceptions can be declared using commas.

public void process() throws IOException, SQLException { }

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✅ 4. Is Throwable a class or an interface? What is its role?

Answer:

Throwable is a class and the superclass of Exception and Error.

It is the root of Java's exception hierarchy.

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✅ 5. Can we catch Throwable in a catch block?

Answer:

Yes. Catching Throwable lets you catch all exceptions and errors, but it's not recommended because it may also catch fatal errors (OutOfMemoryError, etc.).

catch (Throwable t) {

    t.printStackTrace();

}

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✅ 6. What happens if we declare an exception using throws but don't actually throw it?

Answer:

The code will compile and run fine, but it’s unnecessary.

Declaring without throwing has no effect.

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✅ 7. Can we use throws for unchecked exceptions?

Answer:

Yes, but it's optional. Unchecked exceptions (RuntimeException and its subclasses) do not require throws declaration.

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