Fix checkstyle issues in LZW and ArithmeticCoding classes

Author: enqneres

src/main/java/com/thealgorithms/compression/ArithmeticCoding.java

@@ -9,6 +9,10 @@
 
 public class ArithmeticCoding {
 
+    private ArithmeticCoding() {
+        throw new UnsupportedOperationException("Utility class");
+    }
+
     public static double encode(String input, Map<Character, Double> probabilities) {
         double low = 0.0;
         double high = 1.0;

src/main/java/com/thealgorithms/compression/LZW.java

@@ -1,6 +1,9 @@
 package com.thealgorithms.compression;
 
-import java.util.*;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
 
 /**
  * Implementation of LZW (Lempel–Ziv–Welch) compression algorithm.
@@ -9,6 +12,10 @@
 
 public class LZW {
 
+    private LZW() {
+        throw new UnsupportedOperationException("Utility class");
+    }
+
     public static List<Integer> compress(String input) {
         int dictSize = 256;
         Map<String, Integer> dictionary = new HashMap<>();
@@ -36,4 +43,4 @@ public static List<Integer> compress(String input) {
 
         return result;
     }
-}
+}