modifying ListOfThree class

core-java-modules/core-java-lang-oop-2/src/main/java/com/baeldung/accessmodifiers/publicmodifier/ListOfThree.java

@@ -1,31 +1,31 @@
 package com.baeldung.accessmodifiers.publicmodifier;
 
 import java.util.AbstractList;
+import java.util.Arrays;
 
 public class ListOfThree<E> extends AbstractList<E> {
 
-    private static final int MAX_LENGTH = 3;
-    private int size;
-    private Object[] elements = new Object[MAX_LENGTH];
+    private static final int LENGTH = 3;
+    private Object[] elements;
+    
+    public ListOfThree(E[] data) {
+        if(data == null 
+            || data.length != LENGTH)
+            throw new IllegalArgumentException();
+        
+        this.elements = Arrays.copyOf(data, data.length); //shallow copy
+        
+    }
     
     @Override
     @SuppressWarnings("unchecked")
-    public E get(int index) {        
+    public E get(int index) {      
         return (E)elements[index];
     }
-
-    @Override
-    public boolean add(E e) {
-        
-        elements[size] = e;
-        size++;
-        
-        return true;
-    }
     
     @Override
     public int size() {
-        return size;
+        return LENGTH;
     }
 
 }