Java Exceptions

When executing Java code, different errors can occur: coding errors made by the programmer, errors due to wrong input, or other unforeseeable things.

When an error occurs, Java will normally stop and generate an error message. The technical term for this is: Java will throw an exception (throw an error).

Java try and catch

The try statement allows you to define a block of code to be tested for errors while it is being executed.

The catch statement allows you to define a block of code to be executed, if an error occurs in the try block.

The try and catch keywords come in pairs:

Syntax

Consider the following example:

This will generate an error, because myNumbers[10] does not exist.

The output will be something like this:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 10
        at Main.main(Main.java:4)

 

If an error occurs, we can use try...catch to catch the error and execute some code to handle it:

Example

The output will be:

Something went wrong.

 

Finally

The finally statement lets you execute code, after try...catch, regardless of the result:

Example