Arraylist Slicing

ArrayList slicing allows you to extract a portion of an ArrayList.

It takes two parameters: the starting index and how many elements must be sliced. It returns a new List containing the extracted portion.

ArrayList.slice returns a List instance.

Sublist Between Specified Indices

ArrayList<String> animals = new ArrayList<>(); animals.add("cat"); animals.add("dog"); animals.add("fish"); animals.add("turtle"); animals.add("parrot"); List<String> slicedAnimals = animals.subList(1, 4); System.out.println(slicedAnimals);

Output:

[dog, fish, turtle]

In this example, animals.subList(1, 4) skips the first element of the ArrayList - 'cat'.

Afterwards, it takes the rest of the ArrayList until it reaches the 4th element - 'dog', 'fish', and 'turtle'.

Excluding the last couple of elements:

ArrayList<String> colors = new ArrayList<>(); colors.add("red"); colors.add("green"); colors.add("blue"); colors.add("pink"); colors.add("gray"); colors.add("purple"); colors.add("white"); List<String> slicedColors = colors.subList(0, colors.size() - 2); System.out.println(slicedColors);

Output:

[red, green, blue, pink, gray]

This example takes all elements (starting from index 0) and excludes the last 2 elements specified by colors.size() - 2.

In this case colors has 7 elements. So colors.size() - 2 is the same as 7 - 2 which is 5.

Selecting the last couple of elements:

ArrayList<String> colors = new ArrayList<>(); colors.add("red"); colors.add("green"); colors.add("blue"); colors.add("pink"); colors.add("gray"); colors.add("purple"); colors.add("white"); List<String> slicedColors = colors.subList(colors.size() - 3, colors.size()); System.out.println(slicedColors);

Output:

[gray, purple, white]

This is the same as:

ArrayList<String> colors = new ArrayList<>(); colors.add("red"); colors.add("green"); colors.add("blue"); colors.add("pink"); colors.add("gray"); colors.add("purple"); colors.add("white"); List<String> slicedColors = colors.subList(4, 7); System.out.println(slicedColors);

Output:

[gray, purple, white]

Removing Sublist

A sublist inside an ArrayList can be removed.

ArrayList<String> colors = new ArrayList<>(); colors.add("red"); colors.add("green"); colors.add("blue"); colors.add("pink"); colors.add("gray"); colors.add("purple"); colors.add("white"); colors.subList(2, 5).clear(); System.out.println(colors);

Output:

[red, green, purple, white]

subList(2, 5) selects the folllowing sublist - [blue, pink, gray]

The clear function removes the elements of the sublist.

After removing the sublist elements, the only left elements are - [red, green, purple, white].

Invalid cases

Invalid cases cause error. Such cases are accessing index outside of the ArrayList bounds.

Example:

ArrayList<String> colors = new ArrayList<>(); colors.add("red"); colors.add("green"); colors.add("blue"); colors.add("pink"); colors.add("gray"); colors.add("purple"); colors.add("white"); colors.subList(0, 15);

In this example 15 is outside of the ArrayList bounds.

Another case for index being outside of the ArrayList bounds is using negative indexes such as colors.subList(0, -3);.