Types of Errors

errors

Errors may be classified into two categories:

Compile-Time Errors: All syntax errors are detected and displayed by the Java compiler and hence these errors are known as compile-time errors. Whenever the compiler displays an error, it will not create the .class file. Therefore, it is necessary that we fix all the errors before we can successfully compile and run the program.
Run-Time Errors: Sometimes, a program may compile successfully creating .class file but it may not run properly. Such programs may produce incorrect output due to wrong logic or may terminate due to errors such as stack overflow. Most common run-time errors are:

Dividing an integer by zero
Accessing an element that is out of the bounds of an array
Trying to store a value into an array of an incompatible class
Passing a parameter that is not in a valid range or value for a method
Trying to illegally change the state of a thread
Attempting to use a negative size for an array
Using a null object reference as a legitimate object reference to access a method or a variable
Converting invalid string to a number

When such errors are encountered, Java typically generates an error message and aborts the program.

An exception is a condition caused by a run-time error in the program. When the Java interpreter encounters an error such as dividing an integer by zero, it creates and throws an exception object (i.e., informs us that an error has occurred).
If we want our program to continue with the execution of the remaining code, then we should try to catch the exception object thrown by the error condition and then display an appropriate message for taking corrective actions. This task is known as exception handling.
The purpose of exception handling is to detect and report an “exceptional circumstance” so that appropriate action can be taken. Error handling code performs the following tasks:

Exception type	cause of Exception
ArithmeticException	It is caused by math errors such as division by zero
ArrayIndexOutOfBoundsException	Caused by bad array indexes
ArrayStoreException	Caused when a program tries to store the wrong type of data in an array
FileNotFoundException	Caused by an attempt to access a nonexistent file
IOException	Caused by general I/O failures, such as inability to read from a file
NullPointerException	Caused by referencing a null object
NumberFormatException	Caused when a conversion between strings and number fails
OutOfMemoryException	Caused when there’s not enough memory to allocate a new object
SecurityException	Caused when an applet tries to perform an action not allowed by the browser’s security setting
StackOverflowException	Caused when the system runs out of stack space
StringIndexOutOfBoundsException	Caused when a program attempts to access a nonexistent character position in a string