Add rate limiting code

implementations/java/rate_limiting/LeakyBucket.java

@@ -0,0 +1,42 @@
+package implementations.java.rate_limiting;
+
+import java.time.Instant;
+import java.util.LinkedList;
+import java.util.Queue;
+
+public class LeakyBucket {
+    private final long capacity;        // Maximum number of requests the bucket can hold
+    private final double leakRate;      // Rate at which requests leak out of the bucket (requests per second)
+    private final Queue<Instant> bucket; // Queue to hold timestamps of requests
+    private Instant lastLeakTimestamp;   // Last time we leaked from the bucket
+
+    public LeakyBucket(long capacity, double leakRate) {
+        this.capacity = capacity;
+        this.leakRate = leakRate;
+        this.bucket = new LinkedList<>();
+        this.lastLeakTimestamp = Instant.now();
+    }
+
+    public synchronized boolean allowRequest() {
+        leak();  // First, leak out any requests based on elapsed time
+
+        if (bucket.size() < capacity) {
+            bucket.offer(Instant.now());  // Add the new request to the bucket
+            return true;  // Allow the request
+        }
+        return false;  // Bucket is full, deny the request
+    }
+
+    private void leak() {
+        Instant now = Instant.now();
+        long elapsedMillis = now.toEpochMilli() - lastLeakTimestamp.toEpochMilli();
+        int leakedItems = (int) (elapsedMillis * leakRate / 1000.0);  // Calculate how many items should have leaked
+
+        // Remove the leaked items from the bucket
+        for (int i = 0; i < leakedItems && !bucket.isEmpty(); i++) {
+            bucket.poll();
+        }
+
+        lastLeakTimestamp = now;
+    }
+}