Exception Handling Fundamentals

• Exception handling in Java is managed by five keywords: try, catch, throw, throws and finally.

• These keywords form an interconnected subsystem.

• The instructions to be monitored are inside a try block.

• If an exception occurs in the try block, it will be thrown.

• The code can catch and handle the exception using catch.

• System exceptions are automatically thrown by the Java runtime.

• To throw an exception manually, use the throw keyword.

• Exceptions that come out of a method must be declared with throws.
  The code that needs to be executed when exiting the try block must be placed in a finally block.

Using try and catch

• The try and catch keywords are the basis of exception handling.

• They work together: a catch block can only exist if there is a try block.

• This is the basic format of exception handling blocks in Java.

try {
// block of code whose errors are being monitored
}
catch (TypeExceç1 obEx) {
// handler of TypeExceç1
}
catch (TypeExceç2 obEx) {
// Exceç2Type handler
}

• The type of exception caught by the catch block determines which block will be executed.

• We can have several catch blocks associated with a single try block.

• Only the catch that matches the exception type will be executed, the others will be ignored.

• If no exception is thrown, the try block will be executed normally, and catch blocks will be ignored.

• Since JDK 7, there is try-with-resources, which automatically manages resources as I/O streams.

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