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Last active August 29, 2015 13:57
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Memoizer in JDK 8
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gistfile1.java
public class Memoizer {
public static class MemoizeFunction<T, R> implements Function<T, R> {
private final Map<List, R> cache = new HashMap<>();
private final Function<T, R> function;
public MemoizeFunction(Function<T, R> function) {
Objects.requireNonNull(function);
this.function = function;
}
@Override
public R apply(T t) {
List key = t == null ? Collections.emptyList() : Arrays.asList(t);
return cache.computeIfAbsent(key, list -> function.apply(t));
}
}
public static <T, R> Function<T, R> memoize(Function<T, R> func) {
Objects.requireNonNull(func, "Given function must not be null!");
return new MemoizeFunction<>(func);
}
}
public class MemoizerTest {
@Test
public void memoize() {
Function<Integer, Integer> func = Memoizer.memoize((Integer i) -> i + 1);
assertEquals(Integer.valueOf(3), func.apply(2));
assertEquals(Integer.valueOf(3), func.apply(2));
assertEquals(Integer.valueOf(4), func.apply(3));
}
}
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