Let's not look at the last item which is item 61 and it says throw exceptions it properly to the obstruction 2
. 3
So let's go ahead and look at this item in code. 4
What does item say is that in a multi-year system where we have multiple layers like the higher level 5
they are under lower level years. 6
Unbe how higher level methods in working lower level methods. 7
And if a higher level method catches an exception from a lower level then instead of propagating that 8
exception it should to a new exception that is more meaningful in terms of higher level abstraction 9
. 10
This way higher level layer is not polluted with lower level digger's and this idiom is referred to 11
as exception translation. 12
And we have already done exception translation for example here in our API parser class. 13
If we assume that this is a higher level higher level higher and the lower level layer would be the 14
partially emitted from the indigent class. 15
Understanding the number format exception which is a lower level exception. 16
So here we are catching this exception and in its place we are generating this higher level exception 17
so that exception translation. 18
So here an exceptions do em all. 19
We are just the sheer amateurs if we consider it as as the next higher level. 20
So it is handling the higher level exception. 21
Had we not done that and if we had propagated the number format exception then this higher level field 22
would be polluted with the lower level details like the API like the number format exception and that 23
would be confusing to anybody viewing this particularly or against somebody if somebody is viewing the 24
social good it would be confusing to them as it's a higher level layer. 25
And it's. 26
And they are looking at some really low level exceptions. 27
So that would be confusing to them. 28
So that's basically exception translation. 29
So that's good but also it should not be are used. 30
OK so first we should try to prevent the lower level exception itself in this case it's not possible 31
because it's because of an error from the partners website it's because of that ad done by the partners 32
or by our partners. 33
So it's not preventable. 34
But if it's not preventable we should at least see if it can be handled. 35
OK. 36
Now if it cannot also be handled then we can do exception translation. 37
But in some cases even the lower level exception might be appropriate to higher levels. 38
OK. 39
In that case it is fine to propagate them only if it's not possible if they are not appropriate in that 40
situation. 41
We can do an exception translation. 42
No sometimes a programmer debugging the program might want to know the exact cause behind the generation 43
of the higher level exception. 44
In this case it would be helpful for the programmer to allow access to the lower level exception. 45
And this can be done by a special form of exception translation Karla's exception Cheney. 46
So similar to a detail message. 47
The higher level exception and can encapsulate the low level exception. 48
Let's see how that's how that can be done. 49
So here we have the higher level exception API for matchin exception. 50
And let's see how we can. 51
Encapsulate it at a lower level exception. 52
So let's go back to its class. 53
Let's add a new parameter of pipe towable. 54
It's called Just cause it's the right named reuse. 55
So you might have guessed already that this would be the lower level exception. 56
Now let's pass it to the constructor. 57
So here we are in Woking the superclass constructor. 58
So let's just look at the constructor here. 59
And you said Jenrette construct some superclass as you can see there is this constructor called which 60
is taking two parameters one is the daily message. 61
Another one is the actual costs which would be the low of an exception. 62
It's a global 63
it's goodbye to appear here and it's past the lower level exception which is you 64
know go into exceptions all and just execute this. 65
So as you can see when we do have Prince diopters on the higher level exception it's printing both the 66
higher level stackers which is here API format and it's also printing printing the lower level exception 67
right here. 68
Now if the programmer wishes to see only the low level exception not the higher level then there is 69
this method called Get Gause so it can be invoked on the higher level exception which is easier and 70
so good Cause we're ordered not to doable. 71
And if we invoke the French doctoress mattered it would render a lower level exception. 72
So it would just present only the lower overload exhibition as you can see here. 73
So that's basically exception chinning but in some situations some classes some exception classes might 74
not have such kind of fat changing over constructor. 75
So and that is there is a way we can get off. 76
So let's just remove that little story Muga heart. 77
Now here there is a method called dot in it cause and we can use that. 78
But if that were true that would talk through obol. 79
So in which case this who you know in which case we would have to specify that through obal in the throws 80
clause and we don't want to do that because we want to try only as specific exceptions as possible. 81
Right. 82
So we what we don't want to do something that are generic. 83
So that's why we will we know we were dig this out from here. 84
We're in a new statement here. 85
So create an exception object here let's see event 86
. 87
Sorry this needs to be easy and we're just simply throwing even so we are still throwing a higher level 88
exception. 89
It's just that it. 90
We are passing the lower level exception using the in it costs because we don't have the constructor 91
chaining of a constructor in our class. 92
So that's it. 93
Now once again if you go here and if you execute it are you just going to print the costs. 94
So that's about it. 95
You can also take a look at the supplementary notes on. 96
I'm going to include some key points from the item so you can also read the item itself if you have 97
the book. 98
Otherwise you can just look at the key points. 99
Mostly it's just what are we covered here in the class and that's it. 100
That's it. 101
I know you can also find updated code in the resources section. 102
Thank you. 103
And happy coding