When you catch an exception, what method can you use to get the type of the exception?
Throwing Exceptions in JavaIt is important to understand how to throw exceptions in Java. This will allow you to create higher quality code where errors are checked at compile time instead of runtime, and create custom exceptions that make debugging and recovery easier. Show
Install the Java SDK to identify and fix exceptions How to throw exceptions in JavaThrowing
an exception is as simple as using the "throw" statement. You then specify the
It’s limiting to use a generic exception because it makes it difficult for the calling code to catch it. It’s better to throw custom exceptions, which we will come back to in a bit. Using the Throws keyword
The throws keyword allows the compiler to help you write code that handles this type of error, but it does not prevent the abnormal termination of the program. With the help of the
In the above syntax, exception_list is a comma-separated list of all the exceptions a method might throw. For example:
In the example below, we have created a test method to demonstrate throwing an exception. The
This must be handled with a try/catch block:
The Exception classTo use exceptions within your application more effectively, it is important to understand how to create and throw your own. But before we get into throwing exceptions, let’s first take under the hood: We’ll describe what an exception is and how to define your own, starting with the global exception class that all Java exceptions stem from:
The Types of exceptionsThere are two types of exceptions in Java: checked (compile time) exceptions and unchecked (runtime) exceptions. For clarity, we’ll also discuss how errors are different than exceptions in Java. Checked exception (compile time exception)Checked exceptions must be caught and handled during compile time. If the compiler does not see a
Unchecked exception (runtime exception)Unchecked exceptions do not need to be explicitly handled; they occur at the time of execution, also known as run time. These exceptions can usually be avoided by good coding practices. They are typically caused by programming bugs, such as logic errors or improper use of APIs. These exceptions are ignored at the time of compilation. For example:
The example above will
cause an ErrorsPeople often refer to "errors" and “exceptions” as the same thing colloquially. However, in Java these are separate concepts. Errors are thrown by the Java Virtual Machine and cannot be caught or handled. They derive from java.lang.Error and they occur because of some fault in the environment in which the application is running. For example, stack overflows and out of memory exceptions are environment errors that result in the application exiting. Custom exceptionsJava’s built-in exceptions don’t always provide the information we need. So, we sometimes need to supplement these exceptions with our own. During some specific operation, if an exception occurs in your application, you need to recover and make the user know about it. A custom exception gives you more control to provide extra data about the problem and to handle the exception in your code. The best practice is to extend the
For example, let’s say a program fails to connect to a database. You could use a custom exception to collect information like the database URL, username,
password, etc. In the
How do you catch different types of exceptions?The try-catch is the simplest method of handling exceptions. Put the code you want to run in the try block, and any Java exceptions that the code throws are caught by one or more catch blocks. This method will catch any type of Java exceptions that get thrown. This is the simplest mechanism for handling exceptions.
Which type of exception can a catch clause caught?Each catch block is an exception handler that handles the type of exception indicated by its argument. The argument type, ExceptionType , declares the type of exception that the handler can handle and must be the name of a class that inherits from the Throwable class. The handler can refer to the exception with name .
What are the methods of exception object?When an error occurs within a method, the method creates an object and hands it off to the runtime system. The object, called an exception object, contains information about the error, including its type and the state of the program when the error occurred.
What happens when you catch an exception?When an exception occurs inside a try block, control goes directly to the catch block, so no other code will be executed inside the try block and the value of res will not change. Also when a method throws an exception it does not return anything.
|