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1. What is exception
Abnormality refers to abnormal status or behavior. This includes our human errors in operating the program, etc.
2. What is abnormal operation?
abnormal operation refers to the processing of these error operations.
3, why use exception
1, to avoid feedback errors that cannot be understood and cannot be processed.
2. During the running of the program, it does not affect the operation of other modules.
4. The purpose of learning exceptions is
to catch exceptions and throw exceptions.
5, Java exception mechanism
①throws statement
throws statement handles exceptions from the method/behavior level. Usually the exception we initialize is thrown in the entire method body.
public static void method( ) throws FileNotFoundException, ConnectionException { //code}
example
public class ExceptionBuilder {public static void main(String[] args) throws ClassNotFoundException {Class.forName("234");}}
②try-catch statement
Targeted exception handling, in short, is to handle specific exceptions. The characteristic of
is the independence of exception handling. At the same time, the time complexity and space complexity are improved in both directions.
try {Socket s = new Socket("127.0.0.1", 4555);} catch (IOException e) {e.printStackTrace();}
try statements are placed in the statement block to be executed under normal expected conditions. It is mandatory in the try statement, and the statements in it will be mandatory checked. The
catch statement block is mainly used to handle checked exceptions and undetected exceptions thrown in the try statement block.
③finally statement
finally statement is the statement that is finally executed. It is a block of statements that must be executed regardless of whether the error affects the program.
try {Socket s = new Socket("127.0.0.1", 4555);} catch (IOException e) {e.printStackTrace();} finally {System.out.println("Continue");}
6, exception classification