@Documented @Retention(RetentionPolicy.SOURCE) @Target(ElementType.METHOD) @GroovyASTTransformationClass("org.codehaus.groovy.transform.MemoizedASTTransformation") public @interface Memoized
Method annotation that creates a cache for the results of the execution of the annotated method. Whenever the method is called, the mapping between the parameters and the return value is preserved in a cache making subsequent calls with the same arguments fast.
Example usage:
class MemoizedExample {
@Memoized
int sum(int n1, int n2) {
println "$n1 + $n2 = ${n1 + n2}"
n1 + n2
}
}
which becomes (approximately):
class MemoizedExample {
private final Closure memoizedSum = { int n1, int n2 ->
private$method$memoizedSum(n1,n2)
}.memoize()
int sum(int n1, int n2) {
memoizedSum(n1, n2)
}
private private$method$memoizedSum(int n1, int n2) {
println "$n1 + $n2 = ${n1 + n2}"
n1 + n2
}
}
Upon execution of this code:
def instance = new MemoizedExample() println instance.sum(1, 2) println instance.sum(1, 2) println instance.sum(2, 3) println instance.sum(2, 3)The following will be output:
1 +たす 2 =わ 3 3 3 2 +たす 3 =わ 5 5 5
More examples:
import groovy.transform.*
// Script variable which is changed when increment()
// method is invoked.
// If cached method call is invoked then the value
// of this variable will not change.
@Field boolean incrementChange = false
@Memoized
int increment(int value) {
incrementChange = true
value + 1
}
// Invoke increment with argument 10.
increment(10)
// increment is invoked so incrementChange is true.
assert incrementChange
// Set incrementChange back to false.
incrementChange = false
// Invoke increment with argument 10.
increment(10)
// Now the cached method is used and
// incrementChange is not changed.
assert !incrementChange
// Invoke increment with other argument value.
increment(11)
// increment is invoked so incrementChange is true.
assert incrementChange
| Type | Name and Description |
|---|---|
int |
maxCacheSize The maximum size the cache can grow to. |
int |
protectedCacheSize Number of cached return values to protect from garbage collection. |
The maximum size the cache can grow to.
Number of cached return values to protect from garbage collection.