![]() In this example we do not really care about the exception, but we do print a message to the user about it. ![]() We handle the exception by wrapping the code into a try-catch block. In fact, as described in the javadocs, one could argue that a String of 55 0s should parse to 0. This kind of exception has to be handled. I just reread the javadocs for Integer.parseInt() yet again, and I do not see anything saying 'this doesn't parse negative numbers' (in fact, it says 'signed int'), or, at least explicitly, 'this doesn't parse bit patterns'. Reading a file can throw an exception - for example, the file might not exist or the program does not have read rights to the file. It might contain a number of the correct type that is out of range (such as an integer that is larger than INTMAX ). The code below reads the file given to it as a parameter line by line. We can handle exceptions by wrapping the code into a try-catch block or throwing them out of the method. There are exceptions we have to handle, and exceptions we do not have to handle. There are roughly two categories of exceptions. Methods and constructors can throw exceptions. If the resources are not closed, the operating system sees them as being in use until the program is closed. Now references to files can "disappear", because we do not need them anymore. The try-with-resources approach is useful for handling resources, because the program closes the used resources automatically. If the string contains characters other than numbers, the : for input string: exception will be thrown. We use the try // do something with the lines Java will always let you know if your code has a statement or an expression which can throw an error you have to prepare for. We do not have to prepare for runtime exceptions, such as the NullPointerException, beforehand. Probably the easiest way to do that is to check if the value returned from Character.digit() is -1 or not and then throw an exception. In certain scenarios, when the String which is being converted to int does not contain a parsable integer, then the NumberFormatException is thrown. Some exceptions we have to always prepare for, such as errors when reading from a file or errors related to problems with a network connection. For example, a program might call a method with a null reference and throw a NullPointerException, or the program might try to refer to an element outside an array and result in an IndexOutOfBoundsException, and so on. String myString '1234' int foo Integer. When program execution ends with an error, an exception is thrown.
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