Questions

what is exception? Unchecked exception vs checked exception final vs finally vs finalize throws vs throw

Exception

        int caseNum = 0;
        try {
            caseNum = scan.nextInt();
        }
        catch(InputMismatchException exception) {
            System.out.println("This is not an integer");
        }

自己做题的时候,写边界条件

  • 有时候返回-1并不合理,所以throw new exception
  • 一般会用这种ArgumentOutOfBoundsException是越界
  • 或者IllegalArgumentException
  • NullPointerException
  • ArithmeticException
  • NUmberformatExpection

try

  • 在try中声明的变量,是local variable

Throwable

  • Errors // errors is non-recoverable exceptions : outofmemoryerror, virtualmachineerror, assertionerrors
  • Exception
  • throw can only throw throwable exception not errors

四种Exception

  • IOException
  • InterruptedException //multithread
  • SqlException
  • RuntimeException //包括上楼那些

two types of exceptions:

  • Checked Exception //expection gererated at compilation time
  • Unchecked Exception //runtime exception, like arimetic exception
public int MySquareRoot(int x) {
    if (x < 0) {
        throw new ArgumentOutOfBoundsException("Must be a non-negative integer");
    }

    //our implementation here

}

Errors

  • In Any Programming Language ,when ever we write a program , we get two types of errors, they are

1)CompileTimeErrors

    SyntaxErrors and Imporper environment result is called CompileTime Errors

SyntaxErrors Occur whenever a statement writen by the programmer cannot be compile by the compiler
Whenever a source code is compiled ,first compiler checks whether a proper environment is available for the jvm or not to execute the byte code which it has generated for the source code.

2)RunTimeErrors/LogicalErrors

a)simplelogicalErrors
b)SeriousLogicalErrors

RuntimeErrors are generated while runing an application
 We can classfied two types of errors
 1)SimpleLogicalErrors
 ================
    Logical errors which can be neglected by the jvm .such errors are known as SimpleLogicalErrors.
eg: int x=100/0;
 2)SeriousLogicalErrors
 ======================
 We cannot handle these exceptions jvm will be handled

In General RunTimeErrors we can called as Exceptions

e.gerMessage()

  • 直接Print e的话,会写出他的class name
  • 用getMessage() 只会打印出想要的信息

pritStackTrace()

  • 打印该exception发生的line
try {

}
catch(Exception e) {
    e.printStackTrace();
}

exit优先级高于finally,finally高于return

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