Exception handling is a critical aspect of Java programming that allows developers to manage errors gracefully. Understanding try-catch blocks, custom exceptions, and best practices is vital for robust application development.
To learn more about exception handling, refer to our article: Exception Handling in Java.
Exception handling in Java is a mechanism to handle runtime errors, allowing the program to continue its execution.
An exception is an event that disrupts the normal flow of a program's execution.
There are two main types of exceptions: checked exceptions and unchecked exceptions.
A checked exception is an exception that must be either caught or declared in the method signature.
public void myMethod() throws IOException {
// code that may throw IOException
}An unchecked exception is an exception that does not need to be declared or caught, typically a subclass of RuntimeException.
try block?The try block is used to enclose code that might throw an exception.
try {
// code that may throw an exception
} catch (ExceptionType e) {
// handle exception
}catch block?The catch block is used to handle the exception thrown by the try block.
try {
int result = 10 / 0;
} catch (ArithmeticException e) {
System.out.println("Cannot divide by zero");
}finally block?The finally block is used to execute code after the try and catch blocks, regardless of whether an exception was thrown.
try {
// code that may throw an exception
} catch (Exception e) {
// handle exception
} finally {
// cleanup code
}catch blocks?Yes, you can have multiple catch blocks to handle different types of exceptions.
try {
// code that may throw an exception
} catch (IOException e) {
// handle IOException
} catch (SQLException e) {
// handle SQLException
}throw statement?The throw statement is used to explicitly throw an exception.
throw new IllegalArgumentException("Invalid argument");throws keyword?The throws keyword is used in a method signature to declare that a method can throw exceptions.
public void myMethod() throws IOException, SQLException {
// code that may throw exceptions
}A custom exception is a user-defined exception that extends the Exception class or one of its subclasses.
class MyCustomException extends Exception {
public MyCustomException(String message) {
super(message);
}
}You can create a custom exception by extending the Exception class and providing a constructor.
class MyException extends Exception {
public MyException(String message) {
super(message);
}
}Exception and Error?Exception is a condition that a program can catch and handle, while Error indicates serious problems that a reasonable application should not try to catch.
try-with-resources statement?The try-with-resources statement automatically closes resources when they are no longer needed.
try (BufferedReader br = new BufferedReader(new FileReader("file.txt"))) {
// read from the file
}try-with-resources?Any resource that implements the AutoCloseable interface can be used in a try-with-resources statement.
If an exception is not caught, it propagates up the call stack and may terminate the program if it reaches the main method.
StackTrace?The StackTrace provides information about the method calls that were active at the time an exception was thrown.
You can print the stack trace of an exception using the printStackTrace() method.
catch (Exception e) {
e.printStackTrace();
}finally block used for?The finally block is used to execute code that must run regardless of whether an exception occurred or not, such as cleanup code.
finally block exist without a try block?No, a finally block must always be associated with a try block.
try block without a catch block?Yes, you can have a try block without a catch block if it is followed by a finally block.
try {
// code that may throw an exception
} finally {
// cleanup code
}throw statement?The throw statement is used to explicitly throw an exception.
throws keyword?The throws keyword is used in a method signature to declare that a method can throw exceptions.
ArithmeticException?ArithmeticException is an unchecked exception that occurs when an exceptional arithmetic condition has occurred, such as division by zero.
NullPointerException?NullPointerException is an unchecked exception that occurs when an application attempts to use null in a case where an object is required.
IOException?IOException is a checked exception that occurs when an input or output operation fails or is interrupted.
FileNotFoundException?FileNotFoundException is a checked exception that occurs when an attempt to open the file denoted by a specified pathname has failed.
SQLException?SQLException is a checked exception that provides information on a database access error or other errors.
ClassNotFoundException?ClassNotFoundException is a checked exception that occurs when an application tries to load a class through its string name but cannot find the definition of the class.
try-catch-finally block?The try-catch-finally block is a combination of try, catch, and finally blocks used for exception handling.
Yes, you can catch multiple exceptions in a single catch block using the pipe operator (|).
try {
// code that may throw an exception
} catch (IOException | SQLException e) {
// handle IOException and SQLException
}throw keyword used for?The throw keyword is used to explicitly throw an exception.
throws keyword used for?The throws keyword is used in a method signature to declare that a method can throw exceptions.
try-with-resources statement?The try-with-resources statement automatically closes resources when they are no longer needed.
try (BufferedReader br = new BufferedReader(new FileReader("file.txt"))) {
// read from the file
}finally block?If an exception is thrown in a finally block, it will override any exception thrown in the try or catch blocks.
finally block without a try block?No, a finally block must always be associated with a try block.
ExceptionInInitializerError?ExceptionInInitializerError is an error that occurs when an exception is thrown during the evaluation of a static initializer or the initialization of a static variable.
StackOverflowError?StackOverflowError is an error that occurs when a stack overflow occurs, typically due to deep or infinite recursion.
OutOfMemoryError?OutOfMemoryError is an error that occurs when the Java Virtual Machine cannot allocate an object because it is out of memory.
try-catch block used for?The try-catch block is used to handle exceptions that may occur during the execution of a block of code.
catch block used for?The catch block is used to handle the exception thrown by the try block.
finally block used for?The finally block is used to execute code that must run regardless of whether an exception occurred or not, such as cleanup code.
try-with-resources statement?The try-with-resources statement automatically closes resources when they are no longer needed.
throw statement?The throw statement is used to explicitly throw an exception.
throws keyword?The throws keyword is used in a method signature to declare that a method can throw exceptions.
try-catch-finally block?The try-catch-finally block is a combination of try, catch, and finally blocks used for exception handling.
Yes, you can catch multiple exceptions in a single catch block using the pipe operator (|).
try {
// code that may throw an exception
} catch (IOException | SQLException e) {
// handle IOException and SQLException
}Exception class?The Exception class is the superclass of all exceptions that can be thrown by the Java Virtual Machine.
RuntimeException class?The RuntimeException class is a subclass of Exception that indicates a problem that occurred during the execution of the program.