Java exeptions
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This document discusses Java exceptions. It defines an exception as an unwanted or unexpected event during program execution. It describes different types of exceptions in Java including checked exceptions, unchecked exceptions, and errors. It explains how to handle exceptions using try/catch blocks and the throws keyword. Finally, it provides examples of exception methods and best practices for using exceptions.
![12/6/19
Exceptions Methods
â
public String getMessage() - returns a detailed message about the exception
that has occurred.
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public Throwable getCause() - returns the cause of the exception as
represented by a Throwable object.
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public void printStackTrace() - prints the result of toString along with the stack
trace.
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public StackTraceElement [] getStackTrace() - returns an array containing each
element on the stack trace.](https://image.slidesharecdn.com/javaexeptionio-191205220144/85/Java-exeptions-6-320.jpg)
Java exeptions
- 2. 12/6/19 What is an Exception? An exception is an unwanted or unexpected event, which occurs during the execution of a program. 2
- 4. 12/6/19 Type of exceptions in Java 1. Checked Exceptions - a checked exception is an exception that is typically a user error or a problem that cannot be foreseen by the programmer. These exceptions cannot simply be ignored at the time of compilation. 2. Unchecked Exceptions - these exceptions are not checked at compile-time so compiler does not check whether the programmer has handled them or not but itâs the responsibility of the programmer to handle these exceptions and provide a safe exit. 3. Errors - these are not exceptions at all, but problems that arise beyond the control of the user or the programmer.
- 5. 12/6/19 Difference between error and exception 1. Errors - indicates serious problems that a reasonable application should not try to catch. 2. Exceptions - indicates conditions that a reasonable application might want to catch. Demo â https://www.geeksforgeeks.org/errors-v-s-exceptions-in-java/
- 6. 12/6/19 Exceptions Methods â public String getMessage() - returns a detailed message about the exception that has occurred. â public Throwable getCause() - returns the cause of the exception as represented by a Throwable object. â public void printStackTrace() - prints the result of toString along with the stack trace. â public StackTraceElement [] getStackTrace() - returns an array containing each element on the stack trace.
- 7. 12/6/19 Handling Exceptions âą Catching Exceptions â demo âą Multiple catch Blocks â demo try { //Protected code }catch(ExceptionName e1) { //Catch block } try { //Protected code }catch(ExceptionType1 e1) { //Catch block }catch(ExceptionType2 e2) { //Catch block }catch(ExceptionType3 e3) { //Catch block }
- 8. 12/6/19 Handling Exceptions âą Catching multiple type of exceptions â demo âą The throws/throw Keywords â demo catch (IOException|FileNotFoundException ex){ logger.log(ex); throw ex; } import java.io.*; public class className { public void deposit(double amount) throws RemoteException{ // Method implementation throw new RemoteException(); } //Remainder of class definition }
- 9. 12/6/19 Handling Exceptions âą The finally block - a finally block appears at the end of the catch blocks. - demo âą The try-with-resources - demo try { //Protected code }catch(ExceptionType1 e1) { //Catch block }catch(ExceptionType2 e2) { //Catch block }catch(ExceptionType3 e3) { //Catch block }finally { //The finally block always executes. } try(FileReader fr=new FileReader("file path")){ //use the resource }catch(){ //body of catch }
- 10. 12/6/19 Handling Exceptions âą User-defined Exceptions - all exceptions must be a child of Throwable. class MyException extends Exception{ //...... }
- 11. 12/6/19 Best practices âWhen used to best advantage, exceptions can improve a programâs readability, reliability, and maintainability. When used improperly, they can have the opposite effect.â â Effective Java