Merge pull request eugenp#8087 from mona-mohamadinia/BAEL-3398

[BAEL-3398]: Generating Random Dates

Author: sjmillington

core-java-modules/core-java-datetime-java8/src/main/java/com/baeldung/random/LegacyRandomDateTimes.java

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+package com.baeldung.random;
+
+import java.util.Date;
+import java.util.concurrent.ThreadLocalRandom;
+
+public class LegacyRandomDateTimes {
+
+    public static Date between(Date startInclusive, Date endExclusive) {
+        long startMillis = startInclusive.getTime();
+        long endMillis = endExclusive.getTime();
+        long randomMillisSinceEpoch = ThreadLocalRandom.current().nextLong(startMillis, endMillis);
+
+        return new Date(randomMillisSinceEpoch);
+    }
+
+    public static Date timestamp() {
+        return new Date(ThreadLocalRandom.current().nextInt() * 1000L);
+    }
+}

core-java-modules/core-java-datetime-java8/src/main/java/com/baeldung/random/RandomDateTimes.java

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+package com.baeldung.random;
+
+import java.time.Instant;
+import java.util.concurrent.ThreadLocalRandom;
+
+public class RandomDateTimes {
+
+    public static Instant timestamp() {
+        return Instant.ofEpochSecond(ThreadLocalRandom.current().nextInt());
+    }
+
+    public static Instant between(Instant startInclusive, Instant endExclusive) {
+        long startSeconds = startInclusive.getEpochSecond();
+        long endSeconds = endExclusive.getEpochSecond();
+        long random = ThreadLocalRandom.current().nextLong(startSeconds, endSeconds);
+
+        return Instant.ofEpochSecond(random);
+    }
+
+    public static Instant after(Instant startInclusive) {
+        return between(startInclusive, Instant.MAX);
+    }
+
+    public static Instant before(Instant upperExclusive) {
+        return between(Instant.MIN, upperExclusive);
+    }
+}

core-java-modules/core-java-datetime-java8/src/main/java/com/baeldung/random/RandomDates.java

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+package com.baeldung.random;
+
+import java.time.LocalDate;
+import java.util.concurrent.ThreadLocalRandom;
+
+public class RandomDates {
+
+    public static LocalDate between(LocalDate startInclusive, LocalDate endExclusive) {
+        long startEpochDay = startInclusive.toEpochDay();
+        long endEpochDay = endExclusive.toEpochDay();
+        long randomDay = ThreadLocalRandom.current().nextLong(startEpochDay, endEpochDay);
+
+        return LocalDate.ofEpochDay(randomDay);
+    }
+
+    public static LocalDate date() {
+        int hundredYears = 100 * 365;
+        return LocalDate.ofEpochDay(ThreadLocalRandom.current().nextInt(-hundredYears, hundredYears));
+    }
+}

core-java-modules/core-java-datetime-java8/src/main/java/com/baeldung/random/RandomTimes.java

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+package com.baeldung.random;
+
+import java.time.LocalTime;
+import java.util.concurrent.ThreadLocalRandom;
+
+public class RandomTimes {
+
+    public static LocalTime between(LocalTime startTime, LocalTime endTime) {
+        int startSeconds = startTime.toSecondOfDay();
+        int endSeconds = endTime.toSecondOfDay();
+        int randomTime = ThreadLocalRandom.current().nextInt(startSeconds, endSeconds);
+
+        return LocalTime.ofSecondOfDay(randomTime);
+    }
+
+    public static LocalTime time() {
+        return between(LocalTime.MIN, LocalTime.MAX);
+    }
+}

core-java-modules/core-java-datetime-java8/src/test/java/com/baeldung/random/LegacyRandomDateTimesUnitTest.java

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+package com.baeldung.random;
+
+import org.junit.jupiter.api.RepeatedTest;
+
+import java.util.Date;
+import java.util.concurrent.TimeUnit;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class LegacyRandomDateTimesUnitTest {
+
+    private static final Date MIN_DATE = new Date(Long.MIN_VALUE);
+    private static final Date MAX_DATE = new Date(Long.MAX_VALUE);
+
+    @RepeatedTest(100)
+    void givenARange_WhenGenTimestamp_ShouldBeInRange() {
+        long aDay = TimeUnit.DAYS.toMillis(1);
+        long now = new Date().getTime();
+
+        Date hundredYearsAgo = new Date(now - aDay * 365 * 100);
+        Date tenDaysAgo = new Date(now - aDay * 10);
+
+        Date random = LegacyRandomDateTimes.between(hundredYearsAgo, tenDaysAgo);
+        assertThat(random).isBetween(hundredYearsAgo, tenDaysAgo);
+    }
+
+    @RepeatedTest(100)
+    void givenNoRange_WhenGenTimestamp_ShouldGenerateRandomTimestamps() {
+        Date random = LegacyRandomDateTimes.timestamp();
+
+        assertThat(random)
+                .isNotNull()
+                .isBetween(MIN_DATE, MAX_DATE);
+    }
+
+}

core-java-modules/core-java-datetime-java8/src/test/java/com/baeldung/random/RandomDateTimesUnitTest.java

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+package com.baeldung.random;
+
+import org.junit.jupiter.api.RepeatedTest;
+
+import java.time.Duration;
+import java.time.Instant;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class RandomDateTimesUnitTest {
+
+    @RepeatedTest(100)
+    void givenNoRange_WhenGenTimestamp_ShouldGenerateRandomTimestamps() {
+        Instant random = RandomDateTimes.timestamp();
+
+        assertThat(random).isBetween(Instant.MIN, Instant.MAX);
+    }
+
+    @RepeatedTest(100)
+    void givenARange_WhenGenTimestamp_ShouldBeInRange() {
+        Instant hundredYearsAgo = Instant.now().minus(Duration.ofDays(100 * 365));
+        Instant tenDaysAgo = Instant.now().minus(Duration.ofDays(10));
+
+        Instant random = RandomDateTimes.between(hundredYearsAgo, tenDaysAgo);
+        assertThat(random).isBetween(hundredYearsAgo, tenDaysAgo);
+    }
+}

core-java-modules/core-java-datetime-java8/src/test/java/com/baeldung/random/RandomDatesUnitTest.java

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+package com.baeldung.random;
+
+import org.junit.jupiter.api.RepeatedTest;
+
+import java.time.LocalDate;
+import java.time.Month;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class RandomDatesUnitTest {
+
+    @RepeatedTest(100)
+    void givenNoRange_WhenGenDate_ShouldGenerateRandomDates() {
+        LocalDate randomDay = RandomDates.date();
+
+        assertThat(randomDay).isAfter(LocalDate.MIN).isBefore(LocalDate.MAX);
+    }
+
+    @RepeatedTest(100)
+    void givenARange_WhenGenDate_ShouldBeInRange() {
+        LocalDate start = LocalDate.of(1989, Month.OCTOBER, 14);
+        LocalDate end = LocalDate.now();
+
+        LocalDate random = RandomDates.between(start, end);
+        assertThat(random).isAfter(start).isBefore(end);
+    }
+}

core-java-modules/core-java-datetime-java8/src/test/java/com/baeldung/random/RandomTimesUnitTest.java

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+package com.baeldung.random;
+
+import org.junit.jupiter.api.RepeatedTest;
+
+import java.time.LocalTime;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class RandomTimesUnitTest {
+
+    @RepeatedTest(100)
+    void givenARange_WhenGenTime_ShouldBeInRange() {
+        LocalTime morning = LocalTime.of(8, 30);
+        LocalTime randomTime = RandomTimes.between(LocalTime.MIDNIGHT, morning);
+
+        assertThat(randomTime)
+                .isAfter(LocalTime.MIDNIGHT).isBefore(morning)
+                .isAfter(LocalTime.MIN).isBefore(LocalTime.MAX);
+    }
+}