Made variables final where possible

src/main/java/com/mojang/brigadier/results/CommandResult.java

@@ -17,7 +17,7 @@ public interface CommandResult {
      * with.
      * @return The combined result
      */
-    default Object combine(Object other) {
+    default Object combine(final Object other) {
         return ListCommandResult.from(this, other);
     }
 
@@ -41,7 +41,7 @@ public interface CommandResult {
      * @param target the object which the source will be combined into
      * @param source the object to combine into the target
      */
-    static Object combine(Object target, Object source) {
+    static Object combine(final Object target, final Object source) {
         if (target instanceof CommandResult) {
             return ((CommandResult)target).combine(source);
         } else if (source instanceof EmptyCommandResult) {

src/main/java/com/mojang/brigadier/results/EmptyCommandResult.java

@@ -13,7 +13,7 @@ public class EmptyCommandResult implements CommandResult {
      * the empty result.
      */
     @Override
-    public Object combine(Object other) {
+    public Object combine(final Object other) {
         return other;
     }
 }

src/main/java/com/mojang/brigadier/results/ListCommandResult.java

@@ -7,14 +7,14 @@ import java.util.ArrayList;
 import java.util.List;
 
 public class ListCommandResult implements CommandResult {
-    private List<Object> results = new ArrayList<>();
+    private final List<Object> results = new ArrayList<>();
 
     public List<Object> getResults() {
         return results;
     }
 
     @Override
-    public ListCommandResult combine(Object other) {
+    public ListCommandResult combine(final Object other) {
         if (!(other instanceof EmptyCommandResult)) {
             results.add(other);
         }
@@ -22,7 +22,7 @@ public class ListCommandResult implements CommandResult {
         return this;
     }
 
-    public static ListCommandResult from(Object a, Object b) {
+    public static ListCommandResult from(final Object a, final Object b) {
         ListCommandResult list = new ListCommandResult();
         list = list.combine(a);
         list = list.combine(b);