Add RandomScheduling algorithm (TheAlgorithms#5810)

Hardvan · web-flow · commit e94be712df05 · 2024-10-29T17:52:37.000Z
diff --git a/DIRECTORY.md b/DIRECTORY.md
@@ -560,6 +560,7 @@
             * [NonPreemptivePriorityScheduling](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/scheduling/NonPreemptivePriorityScheduling.java)
             * [PreemptivePriorityScheduling](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/scheduling/PreemptivePriorityScheduling.java)
             * [ProportionalFairScheduling](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/scheduling/ProportionalFairScheduling.java)
+            * [RandomScheduling](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/scheduling/RandomScheduling.java)
             * [RRScheduling](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/scheduling/RRScheduling.java)
             * [SelfAdjustingScheduling](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/scheduling/SelfAdjustingScheduling.java)
             * [SJFScheduling](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/scheduling/SJFScheduling.java)
@@ -1192,6 +1193,7 @@
             * [NonPreemptivePrioritySchedulingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/scheduling/NonPreemptivePrioritySchedulingTest.java)
             * [PreemptivePrioritySchedulingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/scheduling/PreemptivePrioritySchedulingTest.java)
             * [ProportionalFairSchedulingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/scheduling/ProportionalFairSchedulingTest.java)
+            * [RandomSchedulingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/scheduling/RandomSchedulingTest.java)
             * [RRSchedulingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/scheduling/RRSchedulingTest.java)
             * [SelfAdjustingSchedulingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/scheduling/SelfAdjustingSchedulingTest.java)
             * [SJFSchedulingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/scheduling/SJFSchedulingTest.java)
diff --git a/src/main/java/com/thealgorithms/scheduling/RandomScheduling.java b/src/main/java/com/thealgorithms/scheduling/RandomScheduling.java
@@ -0,0 +1,45 @@
+package com.thealgorithms.scheduling;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+import java.util.Random;
+
+/**
+ * RandomScheduling is an algorithm that assigns tasks in a random order.
+ * It doesn't consider priority, deadlines, or burst times, making it
+ * inefficient but useful in scenarios where fairness or unpredictability
+ * is required (e.g., load balancing in distributed systems).
+ *
+ * Use Case: Distributed systems where randomness helps avoid task starvation.
+ *
+ * @author Hardvan
+ */
+public final class RandomScheduling {
+
+    private final List<String> tasks;
+    private final Random random;
+
+    /**
+     * Constructs a new RandomScheduling instance.
+     *
+     * @param tasks A collection of task names to be scheduled.
+     * @param random A Random instance for generating random numbers.
+     */
+    public RandomScheduling(Collection<String> tasks, Random random) {
+        this.tasks = new ArrayList<>(tasks);
+        this.random = random;
+    }
+
+    /**
+     * Schedules the tasks randomly and returns the randomized order.
+     *
+     * @return A list representing the tasks in their randomized execution order.
+     */
+    public List<String> schedule() {
+        List<String> shuffledTasks = new ArrayList<>(tasks);
+        Collections.shuffle(shuffledTasks, random);
+        return shuffledTasks;
+    }
+}
diff --git a/src/test/java/com/thealgorithms/scheduling/RandomSchedulingTest.java b/src/test/java/com/thealgorithms/scheduling/RandomSchedulingTest.java
@@ -0,0 +1,93 @@
+package com.thealgorithms.scheduling;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.mockito.Mockito.anyInt;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+import java.util.List;
+import java.util.Random;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+public class RandomSchedulingTest {
+
+    private RandomScheduling randomScheduling;
+    private Random mockRandom;
+
+    @BeforeEach
+    public void setup() {
+        mockRandom = mock(Random.class); // Mocking Random for predictable behavior
+    }
+
+    @Test
+    public void testRandomOrder1() {
+        // Arrange
+        List<String> tasks = List.of("Task1", "Task2", "Task3");
+        // Mock the random sequence to control shuffling: swap 0 <-> 1, and 1 <-> 2.
+        when(mockRandom.nextInt(anyInt())).thenReturn(1, 2, 0);
+        randomScheduling = new RandomScheduling(tasks, mockRandom);
+
+        // Act
+        List<String> result = randomScheduling.schedule();
+
+        // Assert
+        assertEquals(List.of("Task1", "Task2", "Task3"), result);
+    }
+
+    @Test
+    public void testRandomOrder2() {
+        // Arrange
+        List<String> tasks = List.of("A", "B", "C", "D");
+        // Mocking predictable swaps for the sequence: [C, B, D, A]
+        when(mockRandom.nextInt(anyInt())).thenReturn(2, 1, 3, 0);
+        randomScheduling = new RandomScheduling(tasks, mockRandom);
+
+        // Act
+        List<String> result = randomScheduling.schedule();
+
+        // Assert
+        assertEquals(List.of("A", "C", "B", "D"), result);
+    }
+
+    @Test
+    public void testSingleTask() {
+        // Arrange
+        List<String> tasks = List.of("SingleTask");
+        when(mockRandom.nextInt(anyInt())).thenReturn(0); // No real shuffle
+        randomScheduling = new RandomScheduling(tasks, mockRandom);
+
+        // Act
+        List<String> result = randomScheduling.schedule();
+
+        // Assert
+        assertEquals(List.of("SingleTask"), result);
+    }
+
+    @Test
+    public void testEmptyTaskList() {
+        // Arrange
+        List<String> tasks = List.of();
+        randomScheduling = new RandomScheduling(tasks, mockRandom);
+
+        // Act
+        List<String> result = randomScheduling.schedule();
+
+        // Assert
+        assertEquals(List.of(), result); // Should return an empty list
+    }
+
+    @Test
+    public void testSameTasksMultipleTimes() {
+        // Arrange
+        List<String> tasks = List.of("X", "X", "Y", "Z");
+        when(mockRandom.nextInt(anyInt())).thenReturn(3, 0, 1, 2);
+        randomScheduling = new RandomScheduling(tasks, mockRandom);
+
+        // Act
+        List<String> result = randomScheduling.schedule();
+
+        // Assert
+        assertEquals(List.of("Y", "X", "X", "Z"), result);
+    }
+}
