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  1. import java.util.AbstractList;
  2. import java.util.Arrays;
  3. import java.util.List;
  4. import java.util.RandomAccess;
  5.  
  6. class Main {
  7.     public static void main(String[] args) {
  8. 		ImmutableList<Integer> list = ImmutableList.create(1, 42);
  9. 		System.out.println(Arrays.asList(1, 42).equals(list));
  10. 	}
  11.  
  12. 	public static final class ImmutableList<E> extends AbstractList<E>
  13. 			implements List<E>, RandomAccess {
  14.  
  15. 		private final transient E[] arrayOfElements;
  16.  
  17. 		/**
  18. 	 * 
  19. 	 */
  20. 		private ImmutableList() {
  21. 			super();
  22. 			arrayOfElements = null;
  23. 		}
  24.  
  25. 		/**
  26. 		 * 
  27. 		 * Constructor with a single element
  28. 		 * 
  29. 		 * @param <E>
  30. 		 *            type of element
  31. 		 * @throws NullPointerException
  32. 		 */
  33. 		private ImmutableList(E element) {
  34. 			super();
  35. 			if (element == null)
  36. 				throw new NullPointerException();
  37.  
  38. 			int i = 0, length = 0;
  39. 			length = (this.arrayOfElements == null ? 1
  40. 					: this.arrayOfElements.length + 1);
  41. 			@SuppressWarnings("unchecked")
  42. 			E[] tempArray = (E[]) new Object[length];
  43.  
  44. 			if (this.arrayOfElements == null) {
  45. 				tempArray[length - 1] = element;
  46. 			} else {
  47. 				for (i = 0; i < tempArray.length; i++) {
  48. 					tempArray[0] = this.arrayOfElements[i];
  49. 				}
  50. 				tempArray[i] = element;
  51. 			}
  52.  
  53. 			this.arrayOfElements = tempArray;
  54. 		}
  55.  
  56. 		/**
  57. 		 * 
  58. 		 * Constructor with an array elements
  59. 		 * 
  60. 		 * @param element
  61. 		 * @throws NullPointerException
  62. 		 */
  63. 		@SafeVarargs
  64. 		private ImmutableList(E... elements) {
  65. 			super();
  66. 			if (elements == null)
  67. 				throw new NullPointerException();
  68. 			this.arrayOfElements = Arrays.copyOf(elements, elements.length);
  69. 		}
  70.  
  71. 		public static <E> ImmutableList<E> create(E element) {
  72. 			return new ImmutableList<E>(element);
  73. 		}
  74.  
  75. 		public static <E> ImmutableList<E> create(E[] arrayofEl) {
  76. 			return new ImmutableList<E>(arrayofEl);
  77. 		}
  78.  
  79. 		@SafeVarargs
  80. 		public static <E> ImmutableList<E> create(E elt, E... arrayOfEl) {
  81. 			@SuppressWarnings("unchecked")
  82. 			E[] tempArray = (E[]) new Object[arrayOfEl.length + 1];
  83. 			tempArray[0] = elt;
  84. 			for (int i = 1; i < tempArray.length; i++) {
  85. 				tempArray[i] = arrayOfEl[i - 1];
  86. 			}
  87. 			return new ImmutableList<E>(tempArray);
  88. 		}
  89.  
  90. 		public static <E> ImmutableList<E> create() {
  91. 			return new ImmutableList<E>();
  92. 		}
  93.  
  94. 		@Override
  95. 		public E get(int index) {
  96. 			return arrayOfElements[index];
  97. 		}
  98.  
  99. 		@Override
  100. 		public int size() {
  101. 			return arrayOfElements.length;
  102. 		}
  103. 	}
  104. }
Success #stdin #stdout 0.06s 215488KB
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https://ideone.com/dnrTwF
language:
Java (12.0.1)
created:
11 years ago
visibility:
public

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