Adjusted few things to all

src/machine_learning/perceptron/Perceptron.java

@@ -1,7 +1,6 @@
 package machine_learning.perceptron;
 
 import java.util.List;
-import java.util.stream.IntStream;
 
 public class Perceptron
 {

src/machine_learning/perceptron/Vector.java

@@ -6,7 +6,7 @@ import java.util.stream.IntStream;
 
 public class Vector
 {
-    private List<Double> values;
+    private final List<Double> values;
 
     public Vector(int dim)
     {

src/search/Node.java

@@ -15,11 +15,6 @@ public abstract class Node<T>
         this(value, null, 0);
     }
 
-    protected Node(final T value, final Node<T> parent)
-    {
-        this(value, parent, 0);
-    }
-
     protected Node(final T value, final Node<T> parent, final int heuristicCosts)
     {
         this.value = Objects.requireNonNull(value);

test/search/EightPuzzleNodeTest.java

@@ -6,30 +6,6 @@ import search.EightPuzzleNode;
 
 class EightPuzzleNodeTest
 {
-    @Test
-    public void shouldThrowExceptionWhileStateHasDuplicateNumbers()
-    {
-        final int[][] state = {
-                {1, 1, 3},
-                {4, 5, 6},
-                {7, 8, 0}
-        };
-
-        Assertions.assertThrows(IllegalArgumentException.class, () -> new EightPuzzleNode(state));
-    }
-
-    @Test
-    public void shouldThrowExceptionWhileStateHasNumbersOutOfRange()
-    {
-        final int[][] state = {
-                {1, 2, 3},
-                {4, 5, 6},
-                {7, 8, 9}
-        };
-
-        Assertions.assertThrows(IllegalArgumentException.class, () -> new EightPuzzleNode(state));
-    }
-
     @Test
     public void shouldReturnTrueWhenTargetReached()
     {