JavaScript方法中“ splice（a，b，…）”的Java等价方法

Question

someArray.splice(a,b,...)JavaScript中的方法在数组中添加项或从数组中删除项。用Java语言实现这种方法的最佳和简单解决方案是什么？假设我们有String[]数组。

Answer 1

这是Array.prototype.splice()根据JavaScript
MDN规范
的方法的Java实现。

  public static <T>T[] splice(final T[] array, int start) {
    if (start < 0)
      start += array.length;

    return splice(array, start, array.length - start);
  }

  @SuppressWarnings("unchecked")
  public static <T>T[] splice(final T[] array, int start, final int deleteCount) {
    if (start < 0)
      start += array.length;

    final T[] spliced = (T[])Array.newInstance(array.getClass().getComponentType(), array.length - deleteCount);
    if (start != 0)
      System.arraycopy(array, 0, spliced, 0, start);

    if (start + deleteCount != array.length)
      System.arraycopy(array, start + deleteCount, spliced, start, array.length - start - deleteCount);

    return spliced;
  }

  @SuppressWarnings("unchecked")
  public static <T>T[] splice(final T[] array, int start, final int deleteCount, final T ... items) {
    if (start < 0)
      start += array.length;

    final T[] spliced = (T[])Array.newInstance(array.getClass().getComponentType(), array.length - deleteCount + items.length);
    if (start != 0)
      System.arraycopy(array, 0, spliced, 0, start);

    if (items.length > 0)
      System.arraycopy(items, 0, spliced, start, items.length);

    if (start + deleteCount != array.length)
      System.arraycopy(array, start + deleteCount, spliced, start + items.length, array.length - start - deleteCount);

    return spliced;
  }

以下JUnit代码测试了此实现：

@Test
  public void testSplice() {
    final String[] array = new String[] {"a", "b", "c", "d", "e", "f"};

    Assert.assertArrayEquals(new String[] {"c", "d", "e", "f"}, Arrays.splice(array, 0, 2));
    Assert.assertArrayEquals(new String[] {"a", "d", "e", "f"}, Arrays.splice(array, 1, 2));
    Assert.assertArrayEquals(new String[] {"a", "b", "e", "f"}, Arrays.splice(array, 2, 2));
    Assert.assertArrayEquals(new String[] {"a", "b", "c", "f"}, Arrays.splice(array, 3, 2));
    Assert.assertArrayEquals(new String[] {"a", "b", "c", "d"}, Arrays.splice(array, 4, 2));
    try {
      Arrays.splice(array, 5, 2);
      Assert.fail("Expected ArrayIndexOutOfBoundsException");
    }
    catch (final ArrayIndexOutOfBoundsException e) {
    }

    try {
      Arrays.splice(array, -2, 3);
      Assert.fail("Expected ArrayIndexOutOfBoundsException");
    }
    catch (final ArrayIndexOutOfBoundsException e) {
    }
    Assert.assertArrayEquals(new String[] {"a", "b", "c", "d"}, Arrays.splice(array, -2, 2));
    Assert.assertArrayEquals(new String[] {"a", "b", "c", "f"}, Arrays.splice(array, -3, 2));
    Assert.assertArrayEquals(new String[] {"a", "b", "e", "f"}, Arrays.splice(array, -4, 2));
    Assert.assertArrayEquals(new String[] {"a", "d", "e", "f"}, Arrays.splice(array, -5, 2));
    Assert.assertArrayEquals(new String[] {"c", "d", "e", "f"}, Arrays.splice(array, -6, 2));
    try {
      Arrays.splice(array, -7, 2);
      Assert.fail("Expected ArrayIndexOutOfBoundsException");
    }
    catch (final ArrayIndexOutOfBoundsException e) {
    }

    Assert.assertArrayEquals(new String[] {}, Arrays.splice(array, 0));
    Assert.assertArrayEquals(new String[] {"a"}, Arrays.splice(array, 1));
    Assert.assertArrayEquals(new String[] {"a", "b"}, Arrays.splice(array, 2));
    Assert.assertArrayEquals(new String[] {"a", "b", "c"}, Arrays.splice(array, 3));
    Assert.assertArrayEquals(new String[] {"a", "b", "c", "d"}, Arrays.splice(array, 4));
    Assert.assertArrayEquals(new String[] {"a", "b", "c", "d", "e"}, Arrays.splice(array, 5));
    Assert.assertArrayEquals(new String[] {"a", "b", "c", "d", "e", "f"}, Arrays.splice(array, 6));
    try {
      Arrays.splice(array, 7);
      Assert.fail("Expected ArrayIndexOutOfBoundsException");
    }
    catch (final ArrayIndexOutOfBoundsException e) {
    }

    Assert.assertArrayEquals(new String[] {"a", "b", "c", "d", "e"}, Arrays.splice(array, -1));
    Assert.assertArrayEquals(new String[] {"a", "b", "c", "d"}, Arrays.splice(array, -2));
    Assert.assertArrayEquals(new String[] {"a", "b", "c"}, Arrays.splice(array, -3));
    Assert.assertArrayEquals(new String[] {"a", "b"}, Arrays.splice(array, -4));
    Assert.assertArrayEquals(new String[] {"a"}, Arrays.splice(array, -5));
    Assert.assertArrayEquals(new String[] {}, Arrays.splice(array, -6));
    try {
      Arrays.splice(array, -7);
      Assert.fail("Expected NegativeArraySizeException");
    }
    catch (final NegativeArraySizeException e) {
    }

    Assert.assertArrayEquals(new String[] {"x", "y", "z", "c", "d", "e", "f"}, Arrays.splice(array, 0, 2, "x", "y", "z"));
    Assert.assertArrayEquals(new String[] {"a", "x", "y", "z", "d", "e", "f"}, Arrays.splice(array, 1, 2, "x", "y", "z"));
    Assert.assertArrayEquals(new String[] {"a", "b", "x", "y", "z", "e", "f"}, Arrays.splice(array, 2, 2, "x", "y", "z"));
    Assert.assertArrayEquals(new String[] {"a", "b", "c", "x", "y", "z", "f"}, Arrays.splice(array, 3, 2, "x", "y", "z"));
    Assert.assertArrayEquals(new String[] {"a", "b", "c", "d", "x", "y", "z"}, Arrays.splice(array, 4, 2, "x", "y", "z"));
    try {
      Arrays.splice(array, 5, 2, "x", "y", "z");
      Assert.fail("Expected ArrayIndexOutOfBoundsException");
    }
    catch (final ArrayIndexOutOfBoundsException e) {
    }

    Assert.assertArrayEquals(new String[] {"a", "b", "c", "d", "x", "y", "z"}, Arrays.splice(array, -2, 2, "x", "y", "z"));
    Assert.assertArrayEquals(new String[] {"a", "b", "c", "x", "y", "z", "f"}, Arrays.splice(array, -3, 2, "x", "y", "z"));
    Assert.assertArrayEquals(new String[] {"a", "b", "x", "y", "z", "e", "f"}, Arrays.splice(array, -4, 2, "x", "y", "z"));
    Assert.assertArrayEquals(new String[] {"a", "x", "y", "z", "d", "e", "f"}, Arrays.splice(array, -5, 2, "x", "y", "z"));
    Assert.assertArrayEquals(new String[] {"x", "y", "z", "c", "d", "e", "f"}, Arrays.splice(array, -6, 2, "x", "y", "z"));
    try {
      Arrays.splice(array, -7, 2, "x", "y", "z");
      Assert.fail("Expected ArrayIndexOutOfBoundsException");
    }
    catch (final ArrayIndexOutOfBoundsException e) {
    }
  }

编辑： 正如@denys-
séguret正确指出的那样，此实现与JavaScript规范不同，因为它不会更改/修改原始数组。而是，此实现返回一个新的数组实例。

编辑： 在给定的Maven存储库中，以下Maven工件可以使用此实现：

<project>
  ...
  <dependencies>
    <dependency>
      <groupId>org.safris.commons</groupId>
      <artifactId>commons-lang</artifactId>
      <version>1.6.4</version>
    </dependency>
  </dependencies>
  ...
  <repositories>
    <repository>
      <id>mvn.repo.safris.org</id>
      <url>http://mvn.repo.safris.org/m2</url>
    </repository>
  </repositories>
  ...
</project>