• 增加
      • add(data)
      • add(index,data)
    • 删
      • remove(data)

    • 查

      • get(index)

        1. /**
        2. * @author chenshun00@gmail.com
        3. * @since 2021/7/21 9:15 下午
        4. */
        5. public class TestArrayList<T> {
        7. private int location = 0;
        9. private Object[] elements;
        11. private int initialCapacity;
        13. public TestArrayList(int initialCapacity) {
        14.    this.initialCapacity = initialCapacity;
        15.    this.elements = new Object[this.initialCapacity];
        16. }
        18. public int size() {
        19.    return location;
        20. }
        22. public void add(T data) {
        23.    checkCapacity();
        24.    elements[location] = data;
        25.    location = location + 1;
        26. }
        28. public void add(int index, T data) {
        29.    checkCapacity();
        30.    System.arraycopy(elements, index, elements, index + 1, location - index);
        31.    elements[index] = data;
        32.    location = location + 1;
        33. }
        35. public boolean contains(T data) {
        36.    for (Object element : elements) {
        37.        if (data.equals(element)) {
        38.            return true;
        39.        }
        40.    }
        41.    return false;
        42. }
        44. public boolean remove(T data) {
        45.    final int length = location;
        46.    int tempIndex = -1;
        47.    for (int i = 0; i < length; i++) {
        48.        final Object element = elements[i];
        49.        if (element.equals(data)) {
        50.            tempIndex = i;
        51.            break;
        52.        }
        53.    }
        54.    if (tempIndex < 0) {
        55.        return false;
        56.    }
        57.    System.arraycopy(elements, tempIndex + 1, elements, tempIndex, length - tempIndex);
        58.    return true;
        59. }
        61. @SuppressWarnings("unchecked")
        62. public T get(int index) {
        63.    return (T) elements[index];
        64. }
        66. private void checkCapacity() {
        67.    boolean shouldResize = location / (initialCapacity * 1f) >= 0.75f;
        68.    if (shouldResize) {
        69.        initialCapacity = initialCapacity << 1;
        70.    }
        71.    Object[] temp = new Object[this.initialCapacity];
        72.    System.arraycopy(elements, 0, temp, 0, location);
        73.    elements = temp;
        74. }
        75. }