checked-exceptions

问题 class throwseg1 { void show() throws Exception { throw new Exception(\"my.own.Exception\"); } void show2() throws Exception // Why throws is necessary here ? { show(); } void show3() throws Exception // Why throws is necessary here ? { show2(); } public static void main(String s[]) throws Exception // Why throws is necessary here ? { throwseg1 o1 = new throwseg1(); o1.show3(); } } Why compiler reports that methods show2() , show3() , and main() have unreported exception Exception that must be

问题 I am new to Java and kind of new to programming (I know diving straight into Java probably wasn\'t the greatest idea.) and I\'ve been getting an error consistently no matter how I try to add a pause in my program. I am doing a simple counting program and want to add a one second delay between each number here is the code I have so far: import java.lang.*; public class Counter { public static void main(String[]args) { int i; for (i = 0; i <= 10; i++) { Thread.sleep(1000); System.out.println(i)

问题 What are the Runtime exceptions and what are Checked/Unchecked Exceptions and difference between Error/Exception.Why these many types? Instead Java may simply follow a simple design(just try/catch all types) to handle an abnormal condition in a program? 回答1: Throwable is at the top off all exceptions. Underneath Throwable you have Error and Exception. Underneath Exception you have RuntimeException. Java has two types of exceptions - checked and unchecked. Checked exceptions are enforced by

问题 For a number of years now I have been unable to get a decent answer to the following question: why are some developers so against checked exceptions? I have had numerous conversations, read things on blogs, read what Bruce Eckel had to say (the first person I saw speak out against them). I am currently writing some new code and paying very careful attention to how I deal with exceptions. I am trying to see the point of view of the \"we don\'t like checked exceptions\" crowd and I still cannot

问题 How can I throw CHECKED exceptions from inside Java 8 streams/lambdas? In other words, I want to make code like this compile: public List<Class> getClasses() throws ClassNotFoundException { List<Class> classes = Stream.of(\"java.lang.Object\", \"java.lang.Integer\", \"java.lang.String\") .map(className -> Class.forName(className)) .collect(Collectors.toList()); return classes; } This code does not compile, since the Class.forName() method above throws ClassNotFoundException , which is checked

问题 In Java (or any other language with checked exceptions), when creating your own exception class, how do you decide whether it should be checked or unchecked? My instinct is to say that a checked exception would be called for in cases where the caller might be able to recover in some productive way, where as an unchecked exception would be more for unrecoverable cases, but I\'d be interested in other\'s thoughts. 回答1: Checked Exceptions are great, so long as you understand when they should be

问题 Joshua Bloch in \" Effective Java \" said that Use checked exceptions for recoverable conditions and runtime exceptions for programming errors (Item 58 in 2nd edition) Let\'s see if I understand this correctly. Here is my understanding of a checked exception: try{ String userInput = //read in user input Long id = Long.parseLong(userInput); }catch(NumberFormatException e){ id = 0; //recover the situation by setting the id to 0 } 1. Is the above considered a checked exception? 2. Is