groovy.transform.Memoized Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package groovy.transform;
import org.codehaus.groovy.transform.GroovyASTTransformationClass;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
* 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 {
*
* {@code @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 + 2 = 3
* 3
* 3
* 2 + 3 = 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
*
*
* @author Andrey Bloschetsov
*/
@java.lang.annotation.Documented
@Retention(RetentionPolicy.SOURCE)
@Target({ ElementType.METHOD })
@GroovyASTTransformationClass("org.codehaus.groovy.transform.MemoizedASTTransformation")
public @interface Memoized {
/**
* Number of cached return values to protect from garbage collection.
*/
int protectedCacheSize() default 0;
/**
* The maximum size the cache can grow to.
*/
int maxCacheSize() default 0;
}