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Why does the compiler allow throws when the method will never throw the Exception
How slow are Java exceptions?The case against checked exceptionsWhy does Java have transient fields?Java: How to throw an Exception to the method caller inside a try catch body?Why does this code using random strings print “hello world”?Missing return statement in a non-void method compilesWhy does the Java compiler allow exceptions to be listed in the throws section that it is impossible for the method to throwWhy is “final” not allowed in Java 8 interface methods?Why is executing Java code in comments with certain Unicode characters allowed?Why is catching checked exceptions allowed for code that does not throw exceptions?
I am wondering why the java compiler allows throws in the method declaration when the method will never throw the Exception. Because "throws" is a way of handling the exception (telling the caller to handle it).
Since there are two ways of handling exception (throws & try/catch). In a try/catch, it doesn't allow the catch of an exception not thrown in the try block but it allows a throws in a method that does may not throw the exception.
private static void methodA()
try
// Do something
// No IO operation here
catch (IOException ex) //This line does not compile because
//exception is never thrown from try
// Handle
private static void methodB() throws IOException //Why does this //compile when excetion is never thrown in function body
//Do Something
//No IO operation
java checked-exceptions
New contributor
add a comment |
I am wondering why the java compiler allows throws in the method declaration when the method will never throw the Exception. Because "throws" is a way of handling the exception (telling the caller to handle it).
Since there are two ways of handling exception (throws & try/catch). In a try/catch, it doesn't allow the catch of an exception not thrown in the try block but it allows a throws in a method that does may not throw the exception.
private static void methodA()
try
// Do something
// No IO operation here
catch (IOException ex) //This line does not compile because
//exception is never thrown from try
// Handle
private static void methodB() throws IOException //Why does this //compile when excetion is never thrown in function body
//Do Something
//No IO operation
java checked-exceptions
New contributor
2
TLDR: it's a design choice, and there isn't right or wrong here.
– yaseco
yesterday
1
As we are not the designers of the language, "why" questions would be hard to answer with anything but speculative, opinion-based answers.
– RealSkeptic
yesterday
I also find the termthrows
to be misleading. I parse it ascould_throw
in my mind now and it seems to fit better with its behaviour.
– Eric Duminil
yesterday
add a comment |
I am wondering why the java compiler allows throws in the method declaration when the method will never throw the Exception. Because "throws" is a way of handling the exception (telling the caller to handle it).
Since there are two ways of handling exception (throws & try/catch). In a try/catch, it doesn't allow the catch of an exception not thrown in the try block but it allows a throws in a method that does may not throw the exception.
private static void methodA()
try
// Do something
// No IO operation here
catch (IOException ex) //This line does not compile because
//exception is never thrown from try
// Handle
private static void methodB() throws IOException //Why does this //compile when excetion is never thrown in function body
//Do Something
//No IO operation
java checked-exceptions
New contributor
I am wondering why the java compiler allows throws in the method declaration when the method will never throw the Exception. Because "throws" is a way of handling the exception (telling the caller to handle it).
Since there are two ways of handling exception (throws & try/catch). In a try/catch, it doesn't allow the catch of an exception not thrown in the try block but it allows a throws in a method that does may not throw the exception.
private static void methodA()
try
// Do something
// No IO operation here
catch (IOException ex) //This line does not compile because
//exception is never thrown from try
// Handle
private static void methodB() throws IOException //Why does this //compile when excetion is never thrown in function body
//Do Something
//No IO operation
java checked-exceptions
java checked-exceptions
New contributor
New contributor
New contributor
asked yesterday
PsyApPsyAp
785
785
New contributor
New contributor
2
TLDR: it's a design choice, and there isn't right or wrong here.
– yaseco
yesterday
1
As we are not the designers of the language, "why" questions would be hard to answer with anything but speculative, opinion-based answers.
– RealSkeptic
yesterday
I also find the termthrows
to be misleading. I parse it ascould_throw
in my mind now and it seems to fit better with its behaviour.
– Eric Duminil
yesterday
add a comment |
2
TLDR: it's a design choice, and there isn't right or wrong here.
– yaseco
yesterday
1
As we are not the designers of the language, "why" questions would be hard to answer with anything but speculative, opinion-based answers.
– RealSkeptic
yesterday
I also find the termthrows
to be misleading. I parse it ascould_throw
in my mind now and it seems to fit better with its behaviour.
– Eric Duminil
yesterday
2
2
TLDR: it's a design choice, and there isn't right or wrong here.
– yaseco
yesterday
TLDR: it's a design choice, and there isn't right or wrong here.
– yaseco
yesterday
1
1
As we are not the designers of the language, "why" questions would be hard to answer with anything but speculative, opinion-based answers.
– RealSkeptic
yesterday
As we are not the designers of the language, "why" questions would be hard to answer with anything but speculative, opinion-based answers.
– RealSkeptic
yesterday
I also find the term
throws
to be misleading. I parse it as could_throw
in my mind now and it seems to fit better with its behaviour.– Eric Duminil
yesterday
I also find the term
throws
to be misleading. I parse it as could_throw
in my mind now and it seems to fit better with its behaviour.– Eric Duminil
yesterday
add a comment |
4 Answers
4
active
oldest
votes
The throws
clause is part of the method's contract. It requires the caller of the method to behave as if the specified exception may be thrown by the method (i.e. either catch the exception or declare their own throws
clause).
It's possible that the initial version of a method does not throw the exception specified in the throws
clause, but a future version can throw it without breaking the API (i.e. any existing code that calls the method will still pass compilation).
The opposite it also possible. If the method used to throw the exception specified in the throws
clause, but a future version of it doesn't throw it anymore, you should keep the throws
clause in order not to break existing code that uses your method.
First example:
Suppose you have this code which uses methodB
:
private static void methodA()
methodB(); // doesn't have throws IOException clause yet
If later you want to change methodB
to throw IOException
, methodA
will stop passing compilation.
Second example:
Suppose you have this code which uses methodB
:
private static void methodA()
try
methodB(); // throws IOException
catch (IOException ex)
If you remove the throws
clause from a future version of methodB
, methodA
won't pass compilation anymore.
This example is not very interesting when methodA
is private
, because it can only be used locally (within the same class, where it's easy to modify all the methods that call it).
However, if it becomes public
, you don't know who uses (or will use) your method, so you have no control of all the code that may break as a result of adding or removing the throws
clause.
And if it's an instance method, there's another reason for allowing the throws
clause even if you don't throw the exception - the method can be overridden, and the overriding method may throw the exception even if the base class implementation does not.
2
The last point about the override should be given more emphasis, IMHO. The notion of "what if functions change" is less concrete than the notion of "even though the parent function would have no reason to throw a particular exceptions, even today's versions of child functions might need to do so.
– supercat
yesterday
@supercat agreed, but the code in the question has static methods, which cannot be overridden, which is why most my answer gives reasons that apply to static methods.
– Eran
yesterday
add a comment |
Because the signature defines the contract of the method. Even if the method doesn't throw an IOException now, maybe it will in the future, and you want to prepare for that possibility.
Suppose you just provide a dummy implementation for the method for now, but you know that, later, the actual implementation will potentially throw an IOException.
If the compiler prevented you from adding this throws clause, you would be forced to rework all the calls (recursively) to that method once you provide the actual implementation of the method.
1
It's debatable whether a private method can be said to have a contract.
– RealSkeptic
yesterday
1
It defines a contract for all the other methods in the class. And these methods might, in turn,want to declare an IOException because they rely on the contract of the private method they call.
– JB Nizet
yesterday
You can also decide to change the return value of a private method. That's also part of the "contract", isn't it? And yet, what you do when that happens is fix the code that calls it. The same could have been done with "throws".
– RealSkeptic
yesterday
I don't see how that relates to the question, which is: why does the compiler allow to have a throws clause for an exception that is not thrown by the method. What's your point? The compiler also allows you to uselong
as the return type even if you only ever return constant values that fit into an int. Why? For the same reason: you define the contract, which is that the method may, now or later, return a long value.
– JB Nizet
yesterday
add a comment |
Keyword throws tells programmer that there could be an IOException happening in the method. Now if you didn't specify try/catch it means that when exception is thrown program will stop working, while in try/catch you handle it by doing something else if thrown exception.
Use throws for readability and specifying the possibility of exception and use try/catch to tell program what to do in case of exception.
New contributor
add a comment |
The methodB throws IOException, so the method calling methodB is responsible for catching the exception which will be thrown by methodB. Try calling methodB from other methods, it will ask you to catch it or re-throw the IOException. Somewhere you will have to catch the IOException in the chain (in try/catch block). So you wont get compile time error.
private void sampleMethod()
try
methodB();
catch (IOException e)
// TODO Auto-generated catch block
e.printStackTrace();
try/catch in methodA admittedly swallows the exception, that means methodA is responsible for catching the exception in try/catch block.
"Every statement in any java program must be reachable i.e every statement must be executable at least once"
So, you will get compiler error as your try block doesn't have any code to cause IOException.
add a comment |
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4 Answers
4
active
oldest
votes
4 Answers
4
active
oldest
votes
active
oldest
votes
active
oldest
votes
The throws
clause is part of the method's contract. It requires the caller of the method to behave as if the specified exception may be thrown by the method (i.e. either catch the exception or declare their own throws
clause).
It's possible that the initial version of a method does not throw the exception specified in the throws
clause, but a future version can throw it without breaking the API (i.e. any existing code that calls the method will still pass compilation).
The opposite it also possible. If the method used to throw the exception specified in the throws
clause, but a future version of it doesn't throw it anymore, you should keep the throws
clause in order not to break existing code that uses your method.
First example:
Suppose you have this code which uses methodB
:
private static void methodA()
methodB(); // doesn't have throws IOException clause yet
If later you want to change methodB
to throw IOException
, methodA
will stop passing compilation.
Second example:
Suppose you have this code which uses methodB
:
private static void methodA()
try
methodB(); // throws IOException
catch (IOException ex)
If you remove the throws
clause from a future version of methodB
, methodA
won't pass compilation anymore.
This example is not very interesting when methodA
is private
, because it can only be used locally (within the same class, where it's easy to modify all the methods that call it).
However, if it becomes public
, you don't know who uses (or will use) your method, so you have no control of all the code that may break as a result of adding or removing the throws
clause.
And if it's an instance method, there's another reason for allowing the throws
clause even if you don't throw the exception - the method can be overridden, and the overriding method may throw the exception even if the base class implementation does not.
2
The last point about the override should be given more emphasis, IMHO. The notion of "what if functions change" is less concrete than the notion of "even though the parent function would have no reason to throw a particular exceptions, even today's versions of child functions might need to do so.
– supercat
yesterday
@supercat agreed, but the code in the question has static methods, which cannot be overridden, which is why most my answer gives reasons that apply to static methods.
– Eran
yesterday
add a comment |
The throws
clause is part of the method's contract. It requires the caller of the method to behave as if the specified exception may be thrown by the method (i.e. either catch the exception or declare their own throws
clause).
It's possible that the initial version of a method does not throw the exception specified in the throws
clause, but a future version can throw it without breaking the API (i.e. any existing code that calls the method will still pass compilation).
The opposite it also possible. If the method used to throw the exception specified in the throws
clause, but a future version of it doesn't throw it anymore, you should keep the throws
clause in order not to break existing code that uses your method.
First example:
Suppose you have this code which uses methodB
:
private static void methodA()
methodB(); // doesn't have throws IOException clause yet
If later you want to change methodB
to throw IOException
, methodA
will stop passing compilation.
Second example:
Suppose you have this code which uses methodB
:
private static void methodA()
try
methodB(); // throws IOException
catch (IOException ex)
If you remove the throws
clause from a future version of methodB
, methodA
won't pass compilation anymore.
This example is not very interesting when methodA
is private
, because it can only be used locally (within the same class, where it's easy to modify all the methods that call it).
However, if it becomes public
, you don't know who uses (or will use) your method, so you have no control of all the code that may break as a result of adding or removing the throws
clause.
And if it's an instance method, there's another reason for allowing the throws
clause even if you don't throw the exception - the method can be overridden, and the overriding method may throw the exception even if the base class implementation does not.
2
The last point about the override should be given more emphasis, IMHO. The notion of "what if functions change" is less concrete than the notion of "even though the parent function would have no reason to throw a particular exceptions, even today's versions of child functions might need to do so.
– supercat
yesterday
@supercat agreed, but the code in the question has static methods, which cannot be overridden, which is why most my answer gives reasons that apply to static methods.
– Eran
yesterday
add a comment |
The throws
clause is part of the method's contract. It requires the caller of the method to behave as if the specified exception may be thrown by the method (i.e. either catch the exception or declare their own throws
clause).
It's possible that the initial version of a method does not throw the exception specified in the throws
clause, but a future version can throw it without breaking the API (i.e. any existing code that calls the method will still pass compilation).
The opposite it also possible. If the method used to throw the exception specified in the throws
clause, but a future version of it doesn't throw it anymore, you should keep the throws
clause in order not to break existing code that uses your method.
First example:
Suppose you have this code which uses methodB
:
private static void methodA()
methodB(); // doesn't have throws IOException clause yet
If later you want to change methodB
to throw IOException
, methodA
will stop passing compilation.
Second example:
Suppose you have this code which uses methodB
:
private static void methodA()
try
methodB(); // throws IOException
catch (IOException ex)
If you remove the throws
clause from a future version of methodB
, methodA
won't pass compilation anymore.
This example is not very interesting when methodA
is private
, because it can only be used locally (within the same class, where it's easy to modify all the methods that call it).
However, if it becomes public
, you don't know who uses (or will use) your method, so you have no control of all the code that may break as a result of adding or removing the throws
clause.
And if it's an instance method, there's another reason for allowing the throws
clause even if you don't throw the exception - the method can be overridden, and the overriding method may throw the exception even if the base class implementation does not.
The throws
clause is part of the method's contract. It requires the caller of the method to behave as if the specified exception may be thrown by the method (i.e. either catch the exception or declare their own throws
clause).
It's possible that the initial version of a method does not throw the exception specified in the throws
clause, but a future version can throw it without breaking the API (i.e. any existing code that calls the method will still pass compilation).
The opposite it also possible. If the method used to throw the exception specified in the throws
clause, but a future version of it doesn't throw it anymore, you should keep the throws
clause in order not to break existing code that uses your method.
First example:
Suppose you have this code which uses methodB
:
private static void methodA()
methodB(); // doesn't have throws IOException clause yet
If later you want to change methodB
to throw IOException
, methodA
will stop passing compilation.
Second example:
Suppose you have this code which uses methodB
:
private static void methodA()
try
methodB(); // throws IOException
catch (IOException ex)
If you remove the throws
clause from a future version of methodB
, methodA
won't pass compilation anymore.
This example is not very interesting when methodA
is private
, because it can only be used locally (within the same class, where it's easy to modify all the methods that call it).
However, if it becomes public
, you don't know who uses (or will use) your method, so you have no control of all the code that may break as a result of adding or removing the throws
clause.
And if it's an instance method, there's another reason for allowing the throws
clause even if you don't throw the exception - the method can be overridden, and the overriding method may throw the exception even if the base class implementation does not.
edited yesterday
answered yesterday
EranEran
290k37477563
290k37477563
2
The last point about the override should be given more emphasis, IMHO. The notion of "what if functions change" is less concrete than the notion of "even though the parent function would have no reason to throw a particular exceptions, even today's versions of child functions might need to do so.
– supercat
yesterday
@supercat agreed, but the code in the question has static methods, which cannot be overridden, which is why most my answer gives reasons that apply to static methods.
– Eran
yesterday
add a comment |
2
The last point about the override should be given more emphasis, IMHO. The notion of "what if functions change" is less concrete than the notion of "even though the parent function would have no reason to throw a particular exceptions, even today's versions of child functions might need to do so.
– supercat
yesterday
@supercat agreed, but the code in the question has static methods, which cannot be overridden, which is why most my answer gives reasons that apply to static methods.
– Eran
yesterday
2
2
The last point about the override should be given more emphasis, IMHO. The notion of "what if functions change" is less concrete than the notion of "even though the parent function would have no reason to throw a particular exceptions, even today's versions of child functions might need to do so.
– supercat
yesterday
The last point about the override should be given more emphasis, IMHO. The notion of "what if functions change" is less concrete than the notion of "even though the parent function would have no reason to throw a particular exceptions, even today's versions of child functions might need to do so.
– supercat
yesterday
@supercat agreed, but the code in the question has static methods, which cannot be overridden, which is why most my answer gives reasons that apply to static methods.
– Eran
yesterday
@supercat agreed, but the code in the question has static methods, which cannot be overridden, which is why most my answer gives reasons that apply to static methods.
– Eran
yesterday
add a comment |
Because the signature defines the contract of the method. Even if the method doesn't throw an IOException now, maybe it will in the future, and you want to prepare for that possibility.
Suppose you just provide a dummy implementation for the method for now, but you know that, later, the actual implementation will potentially throw an IOException.
If the compiler prevented you from adding this throws clause, you would be forced to rework all the calls (recursively) to that method once you provide the actual implementation of the method.
1
It's debatable whether a private method can be said to have a contract.
– RealSkeptic
yesterday
1
It defines a contract for all the other methods in the class. And these methods might, in turn,want to declare an IOException because they rely on the contract of the private method they call.
– JB Nizet
yesterday
You can also decide to change the return value of a private method. That's also part of the "contract", isn't it? And yet, what you do when that happens is fix the code that calls it. The same could have been done with "throws".
– RealSkeptic
yesterday
I don't see how that relates to the question, which is: why does the compiler allow to have a throws clause for an exception that is not thrown by the method. What's your point? The compiler also allows you to uselong
as the return type even if you only ever return constant values that fit into an int. Why? For the same reason: you define the contract, which is that the method may, now or later, return a long value.
– JB Nizet
yesterday
add a comment |
Because the signature defines the contract of the method. Even if the method doesn't throw an IOException now, maybe it will in the future, and you want to prepare for that possibility.
Suppose you just provide a dummy implementation for the method for now, but you know that, later, the actual implementation will potentially throw an IOException.
If the compiler prevented you from adding this throws clause, you would be forced to rework all the calls (recursively) to that method once you provide the actual implementation of the method.
1
It's debatable whether a private method can be said to have a contract.
– RealSkeptic
yesterday
1
It defines a contract for all the other methods in the class. And these methods might, in turn,want to declare an IOException because they rely on the contract of the private method they call.
– JB Nizet
yesterday
You can also decide to change the return value of a private method. That's also part of the "contract", isn't it? And yet, what you do when that happens is fix the code that calls it. The same could have been done with "throws".
– RealSkeptic
yesterday
I don't see how that relates to the question, which is: why does the compiler allow to have a throws clause for an exception that is not thrown by the method. What's your point? The compiler also allows you to uselong
as the return type even if you only ever return constant values that fit into an int. Why? For the same reason: you define the contract, which is that the method may, now or later, return a long value.
– JB Nizet
yesterday
add a comment |
Because the signature defines the contract of the method. Even if the method doesn't throw an IOException now, maybe it will in the future, and you want to prepare for that possibility.
Suppose you just provide a dummy implementation for the method for now, but you know that, later, the actual implementation will potentially throw an IOException.
If the compiler prevented you from adding this throws clause, you would be forced to rework all the calls (recursively) to that method once you provide the actual implementation of the method.
Because the signature defines the contract of the method. Even if the method doesn't throw an IOException now, maybe it will in the future, and you want to prepare for that possibility.
Suppose you just provide a dummy implementation for the method for now, but you know that, later, the actual implementation will potentially throw an IOException.
If the compiler prevented you from adding this throws clause, you would be forced to rework all the calls (recursively) to that method once you provide the actual implementation of the method.
answered yesterday
JB NizetJB Nizet
546k588921018
546k588921018
1
It's debatable whether a private method can be said to have a contract.
– RealSkeptic
yesterday
1
It defines a contract for all the other methods in the class. And these methods might, in turn,want to declare an IOException because they rely on the contract of the private method they call.
– JB Nizet
yesterday
You can also decide to change the return value of a private method. That's also part of the "contract", isn't it? And yet, what you do when that happens is fix the code that calls it. The same could have been done with "throws".
– RealSkeptic
yesterday
I don't see how that relates to the question, which is: why does the compiler allow to have a throws clause for an exception that is not thrown by the method. What's your point? The compiler also allows you to uselong
as the return type even if you only ever return constant values that fit into an int. Why? For the same reason: you define the contract, which is that the method may, now or later, return a long value.
– JB Nizet
yesterday
add a comment |
1
It's debatable whether a private method can be said to have a contract.
– RealSkeptic
yesterday
1
It defines a contract for all the other methods in the class. And these methods might, in turn,want to declare an IOException because they rely on the contract of the private method they call.
– JB Nizet
yesterday
You can also decide to change the return value of a private method. That's also part of the "contract", isn't it? And yet, what you do when that happens is fix the code that calls it. The same could have been done with "throws".
– RealSkeptic
yesterday
I don't see how that relates to the question, which is: why does the compiler allow to have a throws clause for an exception that is not thrown by the method. What's your point? The compiler also allows you to uselong
as the return type even if you only ever return constant values that fit into an int. Why? For the same reason: you define the contract, which is that the method may, now or later, return a long value.
– JB Nizet
yesterday
1
1
It's debatable whether a private method can be said to have a contract.
– RealSkeptic
yesterday
It's debatable whether a private method can be said to have a contract.
– RealSkeptic
yesterday
1
1
It defines a contract for all the other methods in the class. And these methods might, in turn,want to declare an IOException because they rely on the contract of the private method they call.
– JB Nizet
yesterday
It defines a contract for all the other methods in the class. And these methods might, in turn,want to declare an IOException because they rely on the contract of the private method they call.
– JB Nizet
yesterday
You can also decide to change the return value of a private method. That's also part of the "contract", isn't it? And yet, what you do when that happens is fix the code that calls it. The same could have been done with "throws".
– RealSkeptic
yesterday
You can also decide to change the return value of a private method. That's also part of the "contract", isn't it? And yet, what you do when that happens is fix the code that calls it. The same could have been done with "throws".
– RealSkeptic
yesterday
I don't see how that relates to the question, which is: why does the compiler allow to have a throws clause for an exception that is not thrown by the method. What's your point? The compiler also allows you to use
long
as the return type even if you only ever return constant values that fit into an int. Why? For the same reason: you define the contract, which is that the method may, now or later, return a long value.– JB Nizet
yesterday
I don't see how that relates to the question, which is: why does the compiler allow to have a throws clause for an exception that is not thrown by the method. What's your point? The compiler also allows you to use
long
as the return type even if you only ever return constant values that fit into an int. Why? For the same reason: you define the contract, which is that the method may, now or later, return a long value.– JB Nizet
yesterday
add a comment |
Keyword throws tells programmer that there could be an IOException happening in the method. Now if you didn't specify try/catch it means that when exception is thrown program will stop working, while in try/catch you handle it by doing something else if thrown exception.
Use throws for readability and specifying the possibility of exception and use try/catch to tell program what to do in case of exception.
New contributor
add a comment |
Keyword throws tells programmer that there could be an IOException happening in the method. Now if you didn't specify try/catch it means that when exception is thrown program will stop working, while in try/catch you handle it by doing something else if thrown exception.
Use throws for readability and specifying the possibility of exception and use try/catch to tell program what to do in case of exception.
New contributor
add a comment |
Keyword throws tells programmer that there could be an IOException happening in the method. Now if you didn't specify try/catch it means that when exception is thrown program will stop working, while in try/catch you handle it by doing something else if thrown exception.
Use throws for readability and specifying the possibility of exception and use try/catch to tell program what to do in case of exception.
New contributor
Keyword throws tells programmer that there could be an IOException happening in the method. Now if you didn't specify try/catch it means that when exception is thrown program will stop working, while in try/catch you handle it by doing something else if thrown exception.
Use throws for readability and specifying the possibility of exception and use try/catch to tell program what to do in case of exception.
New contributor
New contributor
answered yesterday
IvanMIvanM
173
173
New contributor
New contributor
add a comment |
add a comment |
The methodB throws IOException, so the method calling methodB is responsible for catching the exception which will be thrown by methodB. Try calling methodB from other methods, it will ask you to catch it or re-throw the IOException. Somewhere you will have to catch the IOException in the chain (in try/catch block). So you wont get compile time error.
private void sampleMethod()
try
methodB();
catch (IOException e)
// TODO Auto-generated catch block
e.printStackTrace();
try/catch in methodA admittedly swallows the exception, that means methodA is responsible for catching the exception in try/catch block.
"Every statement in any java program must be reachable i.e every statement must be executable at least once"
So, you will get compiler error as your try block doesn't have any code to cause IOException.
add a comment |
The methodB throws IOException, so the method calling methodB is responsible for catching the exception which will be thrown by methodB. Try calling methodB from other methods, it will ask you to catch it or re-throw the IOException. Somewhere you will have to catch the IOException in the chain (in try/catch block). So you wont get compile time error.
private void sampleMethod()
try
methodB();
catch (IOException e)
// TODO Auto-generated catch block
e.printStackTrace();
try/catch in methodA admittedly swallows the exception, that means methodA is responsible for catching the exception in try/catch block.
"Every statement in any java program must be reachable i.e every statement must be executable at least once"
So, you will get compiler error as your try block doesn't have any code to cause IOException.
add a comment |
The methodB throws IOException, so the method calling methodB is responsible for catching the exception which will be thrown by methodB. Try calling methodB from other methods, it will ask you to catch it or re-throw the IOException. Somewhere you will have to catch the IOException in the chain (in try/catch block). So you wont get compile time error.
private void sampleMethod()
try
methodB();
catch (IOException e)
// TODO Auto-generated catch block
e.printStackTrace();
try/catch in methodA admittedly swallows the exception, that means methodA is responsible for catching the exception in try/catch block.
"Every statement in any java program must be reachable i.e every statement must be executable at least once"
So, you will get compiler error as your try block doesn't have any code to cause IOException.
The methodB throws IOException, so the method calling methodB is responsible for catching the exception which will be thrown by methodB. Try calling methodB from other methods, it will ask you to catch it or re-throw the IOException. Somewhere you will have to catch the IOException in the chain (in try/catch block). So you wont get compile time error.
private void sampleMethod()
try
methodB();
catch (IOException e)
// TODO Auto-generated catch block
e.printStackTrace();
try/catch in methodA admittedly swallows the exception, that means methodA is responsible for catching the exception in try/catch block.
"Every statement in any java program must be reachable i.e every statement must be executable at least once"
So, you will get compiler error as your try block doesn't have any code to cause IOException.
answered yesterday
Harsimran17Harsimran17
92
92
add a comment |
add a comment |
PsyAp is a new contributor. Be nice, and check out our Code of Conduct.
PsyAp is a new contributor. Be nice, and check out our Code of Conduct.
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2
TLDR: it's a design choice, and there isn't right or wrong here.
– yaseco
yesterday
1
As we are not the designers of the language, "why" questions would be hard to answer with anything but speculative, opinion-based answers.
– RealSkeptic
yesterday
I also find the term
throws
to be misleading. I parse it ascould_throw
in my mind now and it seems to fit better with its behaviour.– Eric Duminil
yesterday