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Difference between throw and throws

Popularity：107 ℃/2024-08-17 10:01:47

throw cap (a poem)throws are two keywords related to exception handling in Java, but they have different roles and usage scenarios.
throw Used to actively throw an exception object inside a method. Example:

if (condition) {
    throw new RuntimeException("customized exception message");;
}

throws Then it is used to specify the type of exception that the method may throw at the method declaration. Example:

public void method() throws IOException {
    // The method body, instead of handling an IOException if one is likely to be thrown, declares that it will be thrown.
}

Their main differences include:

  1. Location difference
    • throw Appears inside the method body and is used to throw a specific exception object.
    • throws Appears at the method declaration and lists the types of exceptions that may be thrown by the method.
  2. differ
    • throw Used to actively throw exceptions to interrupt the flow of execution of the current program.
    • throws It just informs the caller that the method may throw these exceptions and the caller needs to handle these possible exceptions.
  3. vary
    • throw Only one exception object can be thrown at a time.
    • throws Multiple exception types can be declared to be thrown, separated by commas.
  4. Differences in treatment
    • insofar asthrow Exceptions thrown that are not caught and handled internally by the method are passed to the higher-level caller.
    • insofar asthrows Declared exceptions, if not handled by the caller, can result in compilation errors.

For example, the following is an example of a comprehensive use ofthrow cap (a poem)throws Examples of:

public class ThrowThrowsExample {

    public static void main(String[] args) {
        try {
            method1();
        } catch (IOException e) {
            ();
        }
    }

    public static void method1() throws IOException {
        if (someCondition) {
            throw new IOException("IO exceptions");
        }
    }
}

In conclusion.throw is used to throw an exception inside a method, whereasthrows Used in method declarations to inform the type of exception that may be thrown. Used appropriately, they allow for effective exception handling and improved code robustness.

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