style: use proper spelling (#5436)

checkstyle: fix typos, style

Co-authored-by: alxkm <alx@alx.com>
Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com>

src/main/java/com/thealgorithms/datastructures/graphs/BipartiteGraphDFS.java

@@ -14,8 +14,8 @@ import java.util.Arrays;
  *
  * Output : YES
  */
-public final class BipartiteGrapfDFS {
-    private BipartiteGrapfDFS() {
+public final class BipartiteGraphDFS {
+    private BipartiteGraphDFS() {
     }
 
     private static boolean bipartite(int v, ArrayList<ArrayList<Integer>> adj, int[] color, int node) {

src/main/java/com/thealgorithms/datastructures/lists/MergeKSortedLinkedList.java

@@ -7,7 +7,7 @@ import java.util.PriorityQueue;
 /**
  * @author Arun Pandey (https://github.com/pandeyarun709)
  */
-public class MergeKSortedLinkedlist {
+public class MergeKSortedLinkedList {
 
     /**
      * This function merge K sorted LinkedList

src/main/java/com/thealgorithms/stacks/LargestRectangle.java

@@ -11,7 +11,7 @@ public final class LargestRectangle {
     private LargestRectangle() {
     }
 
-    public static String largestRectanglehistogram(int[] heights) {
+    public static String largestRectangleHistogram(int[] heights) {
         int n = heights.length;
         int maxArea = 0;
         Stack<int[]> st = new Stack<>();
@@ -32,7 +32,7 @@ public final class LargestRectangle {
     }
 
     public static void main(String[] args) {
-        assert largestRectanglehistogram(new int[] {2, 1, 5, 6, 2, 3}).equals("10");
-        assert largestRectanglehistogram(new int[] {2, 4}).equals("4");
+        assert largestRectangleHistogram(new int[] {2, 1, 5, 6, 2, 3}).equals("10");
+        assert largestRectangleHistogram(new int[] {2, 4}).equals("4");
     }
 }

src/main/java/com/thealgorithms/strings/ReverseWordsInString.java

@@ -13,7 +13,6 @@ public final class ReverseWordsInString {
      * @param s the input string
      * @return A string created by reversing the order of the words in {@code s}
      */
-
     public static String reverseWordsInString(final String s) {
         var words = s.trim().split("\\s+");
         Collections.reverse(Arrays.asList(words));

src/main/java/com/thealgorithms/strings/Upper.java

@@ -15,13 +15,13 @@ public final class Upper {
     }
 
     /**
-     * Converts all of the characters in this {@code String} to upper case
+     * Converts all the characters in this {@code String} to upper case
      *
      * @param s the string to convert
      * @return the {@code String}, converted to uppercase.
      */
     public static String toUpperCase(String s) {
-        if (s == null || "".equals(s)) {
+        if (s == null || s.isEmpty()) {
             return s;
         }
         char[] values = s.toCharArray();