"throw" vs "throws" in Java
throw vs throws
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throw-
The
throwkeyword is used to actually throw an exception object from a method or block of code. - It can throw only one exception object at a time.
- Mostly used for unchecked exceptions but can also throw checked exceptions (requires handling).
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Syntax example :-
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throw new IOException("File not found");
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The
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throws-
The
throwskeyword is used in a method declaration to declare the exceptions that a method might throw. - We can declare one or multiple exceptions, separated by commas.
- Mainly used for checked exceptions, but can also declare unchecked exceptions (not necessary).
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Syntax example :-
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void readFile() throws IOException, SQLException { }
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The
Below are some differences between throw and throws:
| Aspect | throw | throws |
|---|---|---|
| Definition | Used to actually throw an exception object from a method or block of code. | Used in method declaration to declare the exceptions that a method might throw. |
| Usage Location | Inside a method or a block of code. | In method or constructor declaration only. |
| Number of Exceptions | Can throw only one exception object at a time. | Can declare multiple exceptions separated by commas. |
| Checked / Unchecked | Can throw both checked and unchecked exceptions. | Mainly for checked exceptions; can declare unchecked exceptions but not necessary. |
| Effect on Caller | Immediately transfers the exception to the caller. | Informs the caller that it should handle the declared exceptions. |
| Example | throw new IOException("File not found"); |
void readFile() throws IOException, SQLException { } |
| Requirement | Checked exceptions must be handled using try-catch or declared with throws. |
Caller must handle checked exceptions declared with throws. |
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