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Unchecked exceptions happened during the runtime.

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There are two types of exceptions, checked exceptions and unchecked exceptions in the previous lesson,

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you learned to catch checked exceptions, but in this lesson you're going to learn to fix unchecked

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exceptions.

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Both checked and unchecked exceptions are failures.

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I checked exception is a failure that's outside the control of the application, so Java is going to

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force you to try to run the code and catch the exception if it fails.

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An unchecked exception is the result of badly written code, never, ever catch an unchecked exception,

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catching an unchecked exception is the same as sweeping the problem under the rug.

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If your code is badly written, don't cover the problem.

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Instead, fix your code so that it doesn't fail.

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Unchecked exceptions are runtime exceptions.

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In other words, the failure happens while the app is running and will crash your application.

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The most common examples are right index out of bounds.

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Exception, null pointer exception.

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A legal argument.

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Exception in mismatch exception.

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An illegal state exception.

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There are so many more.

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Let's have a look at each one.

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Go to this path in your resources and open unchecked exceptions, and if you're missing this path for

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whatever reason, make sure to download the updated resources from GitHub.

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The array index out of bounds exception is thrown if you index outside the bounds of the array.

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So inside runtime, except you one Java, we're going to try to index the fifth element from an array

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that stores only three elements.

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And it crashes the application, throws an array index out of bounds exception.

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Now, there are two things we can do.

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You can try to run this code.

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And catch the exception if it fails.

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We're going to catch the array index out of bounds exception and print the message that it comes with.

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This time, the application doesn't crash.

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The code fails and throws an exception, but we're catching the exception and printing its message.

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And that being said, never, ever do that, never catch an unchecked exception.

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Remember that catching and unchecked exception is the same as sweeping the problem under the rug.

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When Jova throws an unchecked exception, like a right index out of bounds, that means there's something

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wrong or there's something missing in your code.

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So instead of catching the failure thickset so that it doesn't happen.

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And there you go.

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Now, the null pointer exception is thrown if you try to access something, if you try to dots and tags

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from a null.

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So inside one exception to that job, I try to call a method from the string class, I'm going to call

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a random method like two lowercase.

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And the code in line for fails and throws a null pointer exception, crashing the application, the

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null pointer exception is an unchecked exception because it happens during the runtime and when you

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get an unchecked exception, that means there's something wrong with your code.

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Let's fix it.

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So here I'm going to say if word is equal to null.

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Then I'll print the word is no.

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Otherwise, and only then are we allowed to call were lowercase.

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So as you can see, the unchecked exception forced me to improve my code.

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This was fully within my control.

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And the reason this is being highlighted is because it's never going to run.

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Word is always no.

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So it's that code anyway is not too important.

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But here's a common mistake.

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Normally, you should always use the equals method to compare a string, but you can't use it to check

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for a nail because dots and doxxing from a null trying to access something from a null is always going

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to throw a nail pointer exception.

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All right, let's fix it.

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Never replace if with try catch.

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I have no idea why people do this, if else statements are a lot faster than try catch and they're easier

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to work with.

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Besides only ever use, try and catch to catch the exceptions.

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Now, the input mismatch exceptions thrown by scanner, if the user enters a value that it wasn't expecting.

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So run the code inside runtime, except in three Java.

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Skinner is expecting an integer, but we're going to pass in a string.

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And we get an input mismatch exception, the input mismatch exception is an unchecked exception because

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it was thrown during the runtime.

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When you get an unchecked exception.

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Then there's something wrong or there's something missing in your code.

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In this case, what's missing is code that checks in advance if the next is an integer.

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And only then are we going to pick up the values, scandal and extent.

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Otherwise, we're going to have to pick it up using Scandi next line, because next line can pick up

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anything.

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And also, we'll tell the user.

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Not a no.

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OK, we on the code.

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I'll put in a word, and just like that, we handled the unchecked exception by fixing our code.

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Now we can say the code is reliable because there's no way that it's going to crash no matter what I

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throw at it.

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All right, we can actually take this a step further, we can use a while loop that runs forever.

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If the next input is an integer, then we'll print it and break the loop.

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And if the next input is anything else, then we'll pick it up with next line.

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And now the code is going to keep asking the user to enter a number until they do.

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If you can take anything away from this lesson, take this rule of thumb, catch a exception because

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it's outside the applications control, in any case, Judge is going to force you to catch it before

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compiling thickset, unchecked exception because it implies that there's something wrong or there's

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something missing in your code.

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In this lesson, you fixed three unchecked exceptions, an unchecked exception is a one time exception.

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The failure happens during the runtime because of poorly written code and never catch an unchecked exception.

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Instead, fix the code or improve the code so that the failure doesn't happen.