Java Exception Handling and comparison with C ++ -- Exception classification. Test exceptions. Non-test exceptions. Common exceptions

Like C ++, Java also has some keywords for exception handling. Note: The following two examples only aim to use all keywords as much as possible. To introduce the location of keywords, we do not recommend the following practices. Keyword for exception handling in C ++: try. catch. throw, basic usage example: [cpp] try {throw E;} catch (E e) {} catch (...) {} try {throw E;} catch (E e) {} catch (...) {} throw E throws a defined exception and then catches the exception. Catch (...) is used to handle all exceptions that are not caught above. Keyword for exception handling in Java: try. catch. finally. throw. throws, basic usage example: [java] public void Err () throws E {try {...} catch (E e) {throw e;} finally {...}} public void Err () throws E {try {...} catch (E e) {throw e;} finally {...}} try. catch is similar to C ++, but the catch here does not catch (...), however, there is a finally block, which is a block that will be executed no matter whether there is an exception or whether the exception is captured after the try. In addition, throw is used to throw an exception, and throws is used to explain what exceptions a function may throw. Java Exception classification Throwable -- Exception base class Error -- Throwable subclass, which is usually thrown by a virtual machine. A serious Error occurs. What the program wants to do is to exit safely, and others cannot do anything about Exception -- Throwable subclass, it is generally a Child class of RuntimeException -- Exception caused by a program, an Exception that occurs during running, an array out of bounds, and a null pointer, generally, you can modify the program to avoid non-RuntimeException -- Exception subclasses. IOException and other test exceptions and non-test exceptions. In some cases, these two concepts are very difficult to understand, my personal understanding is: 1. the check exception means that the compiler will check whether you catch the exception. The compiler will force you to write the corresponding catch statement. Otherwise, an error is reported during compilation. These exceptions are generally followed by throws. That is to say, the methods indicate that they may throw an exception. As for the reason why the compiler should do this, it is easy to understand, because I have a method, since I have foreseen that exceptions may be thrown, you have to deal with it, I remind you that something will go wrong. If you don't handle it, what is your concern? All exceptions except the test exceptions belong to this category. 2. A non-checksum exception means that the compiler will not check whether you catch the exception, for example, if the array is out of bounds or a null pointer, the compiler will not take care of you. RuntimeException and Error belong to this type. The above is my understanding. If there are any mistakes, please point them out so that you can correct them in time. Thank you! Common exception cause -- array subscript out-of-bounds ClassCastException ----------- forced conversion failed cause ----- parameter exception cause ----------- NULL pointer exception AssertionError --------------- asserted error predictionininitializererror -- initialization exception StackOverflowError ----------- Stack Overflow