In java we have dedicated API to work with arrays.

• Class:
  • public native boolean isArray();
• Array:
  • public static Object newInstance(Class<?> componentType, int length) - one dimension array
    • 0 < length (otherwise: NegativeArraySizeException)
  • public static Object newInstance(Class<?> componentType, int... dimensions) - at least one dimension array
    • 0 < number of dimensions <= 255
    • NegativeArraySizeException if any dimension < 0
  • public static native int getLength(Object array)
    • IllegalArgumentException if an object is not an array
  • public static native Object get(Object array, int index)
    • IllegalArgumentException if an object is not an array
    • ArrayIndexOutOfBoundsException: if not 0 <= index < length
  • public static native boolean getX(Object array, int index)
    • X - primitive
  • public static native void set(Object array, int index, Object value)
    • IllegalArgumentException if an object argument is not an array, or if the array component type is primitive and an unwrapping conversion fails
    • ArrayIndexOutOfBoundsException: if not 0 <= index < length
  • public static native void setX(Object array, int index, boolean z)
    • X - primitive

We will provide tests for methods mentioned above.

• check if a given object is an array

  Object ints = new int[]{1, 2, 3};
  
  assertTrue(ints.getClass().isArray());
  

• create one dimension

  String[] array = (String[]) Array.newInstance(String.class, 1);
  
  assertThat(array.length, is(1));
  

• create two dimensions

  String[][] array = (String[][]) Array.newInstance(String.class, 1, 1);
  
  assertThat(array.length, is(1));
  assertThat(array[0].length, is(1));
  

• set

  Object array = new String[]{"a"};
  
  Array.set(array, 0, "b");
  
  assertThat(((String[]) array)[0], is("b"));
  

• get

  Object array = new String[]{"a"};
  
  assertThat(Array.get(array, 0), is("a"));
  

• get length of an array

  Object array = new String[]{"a"};
  
  assertThat(Array.getLength(array), is(1));