Retry operation 3 times
Hard
Java
Exceptions
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Problem Statement
Task: call a risky operation and retry up to 3 times on exception. If still fails, throw last exception.
Input Format
A method call that may throw an exception (risky operation).
Output Format
If succeeds within 3 tries → print "Success"
If fails 3 times → throw the last exception
If fails 3 times → throw the last exception
Example
Risky operation fails every time
Exception thrown after 3 attempts
Constraints
• Retry maximum 3 times
• If still failing, rethrow the last exception
• If still failing, rethrow the last exception
Concept Explanation
We attempt the risky operation up to 3 times.
If it succeeds, stop retrying.
If it fails all 3 times, throw the last exception.
If it succeeds, stop retrying.
If it fails all 3 times, throw the last exception.
Step-by-Step Explanation
1.Initialize attempt = 0.
2.Initialize Exception lastException = null.
3.While attempt < 3:
• Try to perform risky operation.
• If success → return.
• If exception occurs:
• Store exception in lastException.
• Increment attempt.
4.After loop ends:
• Throw lastException.
2.Initialize Exception lastException = null.
3.While attempt < 3:
• Try to perform risky operation.
• If success → return.
• If exception occurs:
• Store exception in lastException.
• Increment attempt.
4.After loop ends:
• Throw lastException.
Concept Explanation
We attempt the risky operation up to 3 times.
If it succeeds, stop retrying.
If it fails all 3 times, throw the last exception.
If it succeeds, stop retrying.
If it fails all 3 times, throw the last exception.
Step-by-Step Explanation
1.Initialize attempt = 0.
2.Initialize Exception lastException = null.
3.While attempt < 3:
• Try to perform risky operation.
• If success → return.
• If exception occurs:
• Store exception in lastException.
• Increment attempt.
4.After loop ends:
• Throw lastException.
2.Initialize Exception lastException = null.
3.While attempt < 3:
• Try to perform risky operation.
• If success → return.
• If exception occurs:
• Store exception in lastException.
• Increment attempt.
4.After loop ends:
• Throw lastException.
Input / Output Format
Input Format
A method call that may throw an exception (risky operation).
Output Format
If succeeds within 3 tries → print "Success"
If fails 3 times → throw the last exception
If fails 3 times → throw the last exception
Constraints
• Retry maximum 3 times
• If still failing, rethrow the last exception
• If still failing, rethrow the last exception
Examples
Input:
Risky operation fails every time
Output:
Exception thrown after 3 attempts
Example Solution (Public)
static int retry3(java.util.concurrent.Callable<Integer> op) throws Exception{Exception last=null;for(int i=0;i<3;i++){try{return op.call();}catch(Exception e){last=e;}}throw last;}
Official Solution Code
static int retry3(java.util.concurrent.Callable<Integer> op) throws Exception{Exception last=null;for(int i=0;i<3;i++){try{return op.call();}catch(Exception e){last=e;}}throw last;}
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