BAEL-1464 Guava Memoizer (#3420)

* BAEL-1464 Guava Memoizer * Update codes based on code review and discussion in JIRA
2018-01-29 09:26:15 +01:00
parent 829c0414fe
commit d1a4848cb4
4 changed files with 163 additions and 0 deletions
@@ -0,0 +1,98 @@
+package org.baeldung.guava;
+
+import com.google.common.base.Suppliers;
+import org.baeldung.guava.memoizer.CostlySupplier;
+import org.baeldung.guava.memoizer.Factorial;
+import org.baeldung.guava.memoizer.FibonacciSequence;
+import org.junit.Test;
+
+import java.math.BigInteger;
+import java.time.Duration;
+import java.time.Instant;
+import java.util.concurrent.TimeUnit;
+import java.util.function.Supplier;
+
+import static org.hamcrest.core.Is.is;
+import static org.hamcrest.core.IsEqual.equalTo;
+import static org.hamcrest.number.IsCloseTo.closeTo;
+import static org.junit.Assert.assertThat;
+
+public class GuavaMemoizerUnitTest {
+
+    @Test
+    public void givenInteger_whenGetFibonacciNumber_thenShouldCalculateFibonacciNumber() {
+        // given
+        int n = 95;
+
+        // when
+        BigInteger fibonacciNumber = FibonacciSequence.getFibonacciNumber(n);
+
+        // then
+        BigInteger expectedFibonacciNumber = new BigInteger("31940434634990099905");
+        assertThat(fibonacciNumber, is(equalTo(expectedFibonacciNumber)));
+    }
+
+    @Test
+    public void givenInteger_whenGetFactorial_thenShouldCalculateFactorial() {
+        // given
+        int n = 95;
+
+        // when
+        BigInteger factorial = new Factorial().getFactorial(n);
+
+        // then
+        BigInteger expectedFactorial = new BigInteger("10329978488239059262599702099394727095397746340117372869212250571234293987594703124871765375385424468563282236864226607350415360000000000000000000000");
+        assertThat(factorial, is(equalTo(expectedFactorial)));
+    }
+
+    @Test
+    public void givenMemoizedSupplier_whenGet_thenSubsequentGetsAreFast() {
+        Supplier<BigInteger> memoizedSupplier;
+        memoizedSupplier = Suppliers.memoize(CostlySupplier::generateBigNumber);
+
+        Instant start = Instant.now();
+        BigInteger bigNumber = memoizedSupplier.get();
+        Long durationInMs = Duration.between(start, Instant.now()).toMillis();
+        assertThat(bigNumber, is(equalTo(new BigInteger("12345"))));
+        assertThat(durationInMs.doubleValue(), is(closeTo(2000D, 100D)));
+
+        start = Instant.now();
+        bigNumber = memoizedSupplier.get().add(BigInteger.ONE);
+        durationInMs = Duration.between(start, Instant.now()).toMillis();
+        assertThat(bigNumber, is(equalTo(new BigInteger("12346"))));
+        assertThat(durationInMs.doubleValue(), is(closeTo(0D, 100D)));
+
+        start = Instant.now();
+        bigNumber = memoizedSupplier.get().add(BigInteger.TEN);
+        durationInMs = Duration.between(start, Instant.now()).toMillis();
+        assertThat(bigNumber, is(equalTo(new BigInteger("12355"))));
+        assertThat(durationInMs.doubleValue(), is(closeTo(0D, 100D)));
+    }
+
+    @Test
+    public void givenMemoizedSupplierWithExpiration_whenGet_thenSubsequentGetsBeforeExpiredAreFast() throws InterruptedException {
+        Supplier<BigInteger> memoizedSupplier;
+        memoizedSupplier = Suppliers.memoizeWithExpiration(CostlySupplier::generateBigNumber, 3, TimeUnit.SECONDS);
+
+        Instant start = Instant.now();
+        BigInteger bigNumber = memoizedSupplier.get();
+        Long durationInMs = Duration.between(start, Instant.now()).toMillis();
+        assertThat(bigNumber, is(equalTo(new BigInteger("12345"))));
+        assertThat(durationInMs.doubleValue(), is(closeTo(2000D, 100D)));
+
+        start = Instant.now();
+        bigNumber = memoizedSupplier.get().add(BigInteger.ONE);
+        durationInMs = Duration.between(start, Instant.now()).toMillis();
+        assertThat(bigNumber, is(equalTo(new BigInteger("12346"))));
+        assertThat(durationInMs.doubleValue(), is(closeTo(0D, 100D)));
+
+        TimeUnit.SECONDS.sleep(1);
+
+        start = Instant.now();
+        bigNumber = memoizedSupplier.get().add(BigInteger.TEN);
+        durationInMs = Duration.between(start, Instant.now()).toMillis();
+        assertThat(bigNumber, is(equalTo(new BigInteger("12355"))));
+        assertThat(durationInMs.doubleValue(), is(closeTo(2000D, 100D)));
+    }
+
+}