Exceptions are two kinds:
those are: 1) Checked Exceptions
2)Unchecked Exceptions
Under Unchecked Exceptions there are two kinds are there :
1. Errors
2. Runtime Exceptions
- Exceptions which are detected by Java Compiler at compile time is called Checked Exceptions.These are exceptional conditions that a well-written application should anticipate and recover from.
Example : suppose an application prompts a user for an input file name, then opens the file by passing the name to the constructor for java.io.FileReader.
- Normally, the user provides the name of an existing, readable file, so the construction of the FileReader object succeeds, and the execution of the application proceeds normally.
But sometimes the user supplies the name of a nonexistent file, and the constructor throws java.io.FileNotFoundException. A well-written program will catch this Exception and notify the user of the mistake, possibly prompting for a corrected file name.
- All Exceptions are Checked Exceptions, except for those indicated by Error, RuntimeException, and their subclasses.
Example : suppose an application prompts a user for an input file name, then opens the file by passing the name to the constructor for java.io.FileReader.
- Normally, the user provides the name of an existing, readable file, so the construction of the FileReader object succeeds, and the execution of the application proceeds normally.
But sometimes the user supplies the name of a nonexistent file, and the constructor throws java.io.FileNotFoundException. A well-written program will catch this Exception and notify the user of the mistake, possibly prompting for a corrected file name.
- All Exceptions are Checked Exceptions, except for those indicated by Error, RuntimeException, and their subclasses.
Unchecked Exceptions:
Errors and Runtime Exceptions are collectively known as Unchecked Exceptions.
Errors : These are exceptional conditions that are external to the application, and that the application usually cannot anticipate or recover from.
Example : An application successfully opens a file for input, but is unable to read the file because of a hardware or system malfunction. The unsuccessful read will throw java.io.IOError. An application might choose to catch this exception, in order to notify the user of the problem.
Errors : These are exceptional conditions that are external to the application, and that the application usually cannot anticipate or recover from.
Example : An application successfully opens a file for input, but is unable to read the file because of a hardware or system malfunction. The unsuccessful read will throw java.io.IOError. An application might choose to catch this exception, in order to notify the user of the problem.
- Errors are those exceptions indicated by Error and its SubClasses.
Runtime Exceptions : These are exceptional conditions that are internal to the application, and that the application usually cannot anticipate or recover from. These usually indicate programming bugs, such as logic errors or improper use of an API.
- Runtime Exceptions are those indicated by RuntimeException and its SubClasses.
Example : An application that passes a file name to the constructor for FileReader. If a logic error causes a null to be passed to the constructor, the constructor will throwNullPointerException. The application can catch this exception, but it probably makes more sense to eliminate the bug that caused the exception to occur.
Runtime Exceptions : These are exceptional conditions that are internal to the application, and that the application usually cannot anticipate or recover from. These usually indicate programming bugs, such as logic errors or improper use of an API.
- Runtime Exceptions are those indicated by RuntimeException and its SubClasses.
Example : An application that passes a file name to the constructor for FileReader. If a logic error causes a null to be passed to the constructor, the constructor will throwNullPointerException. The application can catch this exception, but it probably makes more sense to eliminate the bug that caused the exception to occur.
No comments:
Post a Comment