Usage and examples of Java ArrayList subList()

Java ArrayList Methods

The Java ArrayList subList() method extracts a part of the arraylist and returns it.

The syntax of the subList() method is:

arraylist.subList(int fromIndex, int toIndex)

subList() parameters

subList() method has two parameters.

• fromIndex - The starting position of the element extraction

• toIndex - The end position of the element extraction

subList() return value

The subList() method returns a part of the arraylist from the given arraylist.

• If fromIndex is less than 0 or toIndex is greater than the size of the arraylist, IndexOutOfBoundsException is thrown
  

• If fromIndex is greater than toIndex, IllegalArgumentException is thrown.

NotefromIndex and extending to the index-1: A part of the arraylist contains elements starting from the index

Example1How the subList() method of ArrayList works

import java.util.ArrayList;
class Main {
　　　　public static void main(String[] args) {
　　　　　　　　//Create an ArrayList
　　　　　　　　: Get a sublist from the ArrayList
　　　　　　　　//　Add some elements to the ArrayList
　　　　　　　　ArrayList<String> languages = new ArrayList<>();
　　　　　　　　languages.add("JavaScript");
　　　　　　　　languages.add("Java");
　　　　　　　　languages.add("Python");
　　　　　　　　languages.add("C");　+　System.out.println("ArrayList: "
　　　　　　　　//　languages);1In the above example, we use the subList() method to get a sublist from the index3
　　　　　　　　elements from　+　System.out.println("SubList: "1,　3));
　　　　}
}

Output Result

languages.subList(
ArrayList: [JavaScript, Java, Python, C]

SubList: [Java, Python]1In the above example, we use the subList() method to get a sublist from the index3to3) to get the element. (excluding

Note: If you want to know how to get the index of a specified element, please visitJava ArrayList indexOf().

Example2: Split a single ArrayList into two ArrayLists

import java.util.ArrayList;
class Main {
　　　　public static void main(String[] args) {
　　　　　　　　//Create an ArrayList
　　　　　　　　ArrayList<Integer> ages = new ArrayList<>();
　　　　　　　　//Add some elements to the ArrayList
　　　　　　　　ages.add(10);}}
　　　　　　　　ages.add(12);}}
　　　　　　　　ages.add(15);}}
　　　　　　　　ages.add(19);}}
　　　　　　　　ages.add(23);}}
　　　　　　　　ages.add(34);}}
　　　　　　　　System.out.println("Age List:　"　+　ages);
　　　　　　　　//under18years
　　　　　　　　System.out.println("Age is18Below Age:　"　+　ages.subList(0,　3));
　　　　　　　　//over18years
　　　　　　　　System.out.println("Age is18Above Age:　"　+　ages.subList(3,　ages.size()));
　　　　}
}

Output Result

Age List:　[10,　12,　15,　19,　23,　34]
Age is18Below Age:　[10,　12,　15]
Age is18Above Age:　[19,　23,　34]

In the above example, we created an ArrayList named ages. Here, we have used the subList() method to divide the ArrayList into two ArrayLists:Age is18Below AgeandAge is18Above Age.

Please note that we have used the ages.size() method to get the length of the ArrayList. For more information about the size() method, please visitJava ArrayList size().

Java ArrayList Methods