Add FairShareScheduling algorithm (#5815)

Author: Hardvan

DIRECTORY.md

@@ -530,6 +530,7 @@
               * [ScanScheduling](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/scheduling/diskscheduling/ScanScheduling.java)
               * [SSFScheduling](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/scheduling/diskscheduling/SSFScheduling.java)
             * [EDFScheduling](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/scheduling/EDFScheduling.java)
+            * [FairShareScheduling](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/scheduling/FairShareScheduling.java)
             * [FCFSScheduling](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/scheduling/FCFSScheduling.java)
             * [HighestResponseRatioNextScheduling](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/scheduling/HighestResponseRatioNextScheduling.java)
             * [JobSchedulingWithDeadline](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/scheduling/JobSchedulingWithDeadline.java)
@@ -1129,6 +1130,7 @@
               * [ScanSchedulingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/scheduling/diskscheduling/ScanSchedulingTest.java)
               * [SSFSchedulingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/scheduling/diskscheduling/SSFSchedulingTest.java)
             * [EDFSchedulingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/scheduling/EDFSchedulingTest.java)
+            * [FairShareSchedulingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/scheduling/FairShareSchedulingTest.java)
             * [FCFSSchedulingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/scheduling/FCFSSchedulingTest.java)
             * [HighestResponseRatioNextSchedulingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/scheduling/HighestResponseRatioNextSchedulingTest.java)
             * [JobSchedulingWithDeadlineTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/scheduling/JobSchedulingWithDeadlineTest.java)

src/main/java/com/thealgorithms/scheduling/FairShareScheduling.java

@@ -0,0 +1,65 @@
+package com.thealgorithms.scheduling;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * FairShareScheduling allocates CPU resources equally among users or groups
+ * instead of individual tasks. Each group gets a proportional share,
+ * preventing resource hogging by a single user's processes.
+ *
+ * Use Case: Multi-user systems where users submit multiple tasks simultaneously,
+ * such as cloud environments.
+ *
+ * @author Hardvan
+ */
+public final class FairShareScheduling {
+
+    static class User {
+        String name;
+        int allocatedResources;
+        int totalWeight;
+
+        User(String name) {
+            this.name = name;
+            this.allocatedResources = 0;
+            this.totalWeight = 0;
+        }
+
+        void addWeight(int weight) {
+            this.totalWeight += weight;
+        }
+    }
+
+    private final Map<String, User> users; // username -> User
+
+    public FairShareScheduling() {
+        users = new HashMap<>();
+    }
+
+    public void addUser(String userName) {
+        users.putIfAbsent(userName, new User(userName));
+    }
+
+    public void addTask(String userName, int weight) {
+        User user = users.get(userName);
+        if (user != null) {
+            user.addWeight(weight);
+        }
+    }
+
+    public void allocateResources(int totalResources) {
+        int totalWeights = users.values().stream().mapToInt(user -> user.totalWeight).sum();
+        for (User user : users.values()) {
+            user.allocatedResources = (int) ((double) user.totalWeight / totalWeights * totalResources);
+        }
+    }
+
+    public Map<String, Integer> getAllocatedResources() {
+        Map<String, Integer> allocation = new HashMap<>();
+        for (User user : users.values()) {
+            allocation.put(user.name, user.allocatedResources);
+        }
+        return allocation;
+    }
+}

src/test/java/com/thealgorithms/scheduling/FairShareSchedulingTest.java

@@ -0,0 +1,60 @@
+package com.thealgorithms.scheduling;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.Map;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+public class FairShareSchedulingTest {
+
+    private FairShareScheduling scheduler;
+
+    @BeforeEach
+    public void setup() {
+        scheduler = new FairShareScheduling();
+    }
+
+    @Test
+    public void testAllocateResourcesSingleUser() {
+        scheduler.addUser("User1");
+        scheduler.addTask("User1", 5);
+        scheduler.allocateResources(100);
+        Map<String, Integer> expected = Map.of("User1", 100);
+        assertEquals(expected, scheduler.getAllocatedResources());
+    }
+
+    @Test
+    public void testAllocateResourcesMultipleUsers() {
+        scheduler.addUser("User1");
+        scheduler.addUser("User2");
+        scheduler.addUser("User3");
+        scheduler.addTask("User1", 2);
+        scheduler.addTask("User2", 3);
+        scheduler.addTask("User3", 5);
+        scheduler.allocateResources(100);
+        Map<String, Integer> expected = Map.of("User1", 20, "User2", 30, "User3", 50);
+        assertEquals(expected, scheduler.getAllocatedResources());
+    }
+
+    @Test
+    public void testAllocateResourcesZeroWeightUser() {
+        scheduler.addUser("User1");
+        scheduler.addUser("User2");
+        scheduler.addTask("User2", 5);
+        scheduler.allocateResources(100);
+        Map<String, Integer> expected = Map.of("User1", 0, "User2", 100);
+        assertEquals(expected, scheduler.getAllocatedResources());
+    }
+
+    @Test
+    public void testAllocateResourcesEqualWeights() {
+        scheduler.addUser("User1");
+        scheduler.addUser("User2");
+        scheduler.addTask("User1", 1);
+        scheduler.addTask("User2", 1);
+        scheduler.allocateResources(100);
+        Map<String, Integer> expected = Map.of("User1", 50, "User2", 50);
+        assertEquals(expected, scheduler.getAllocatedResources());
+    }
+}