I - the type of the input to the calculationO - the type of the output of the calculationpublic class Memoizer<I,O> extends Object implements Computable<I,O>
Definition of an interface for a wrapper around a calculation that takes a single parameter and returns a result. The results for the calculation will be cached for future requests.
This is not a fully functional cache, there is no way of limiting or removing results once they have been generated. However, it is possible to get the implementation to regenerate the result for a given parameter, if an error was thrown during the previous calculation, by setting the option during the construction of the class. If this is not set the class will return the cached exception.
Thanks should go to Brian Goetz, Tim Peierls and the members of JCP JSR-166 Expert Group for coming up with the original implementation of the class. It was also published within Java Concurrency in Practice as a sample.
| Constructor and Description |
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Memoizer(Computable<I,O> computable)
Constructs a Memoizer for the provided Computable calculation.
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Memoizer(Computable<I,O> computable,
boolean recalculate)
Constructs a Memoizer for the provided Computable calculation, with the
option of whether a Computation that experiences an error should
recalculate on subsequent calls or return the same cached exception.
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public Memoizer(Computable<I,O> computable)
Constructs a Memoizer for the provided Computable calculation.
If a calculation is thrown an exception for any reason, this exception will be cached and returned for all future calls with the provided parameter.
computable - the computation whose results should be memorizedpublic Memoizer(Computable<I,O> computable, boolean recalculate)
Constructs a Memoizer for the provided Computable calculation, with the option of whether a Computation that experiences an error should recalculate on subsequent calls or return the same cached exception.
computable - the computation whose results should be memorizedrecalculate - determines whether the computation should be recalculated on
subsequent calls if the previous call failedpublic O compute(I arg) throws InterruptedException
This method will return the result of the calculation and cache it, if it has not previously been calculated.
This cache will also cache exceptions that occur during the computation
if the recalculate parameter is the constructor was set to
false, or not set. Otherwise, if an exception happened on the
previous calculation, the method will attempt again to generate a value.
compute in interface Computable<I,O>arg - the argument for the calculationInterruptedException - thrown if the calculation is interruptedCopyright © 2001–2017 The Apache Software Foundation. All rights reserved.