Use java's ArrayList.subList() function to obtain the sublist of the specified range of ArrayList

Use java's ArrayList.subList() function to obtain the sublist of the specified range of ArrayList

In Java programming, ArrayList is a very commonly used data structure, which can be used to store a set of data, and can Add or remove elements dynamically. Sometimes, we need to get some elements in the ArrayList, which can be achieved using the subList() function.

The definition of the subList() function is as follows:

List<E> subList(int fromIndex, int toIndex)

Among them, fromIndex represents the starting index (inclusive) of the sublist, toIndex represents the sublist Ending index of the list (exclusive). By calling this function, we can get the sublist from fromIndex to toIndex-1. The returned sublist is a new List instance, which still points to the original ArrayList, and modifications to the sublist will be reflected in the original ArrayList.

The following is a sample code for sublist operation on ArrayList:

import java.util.ArrayList;
import java.util.List;

public class ArrayListExample {

    public static void main(String[] args) {
        // 创建一个包含整数的ArrayList
        ArrayList<Integer> numbers = new ArrayList<>();
        numbers.add(1);
        numbers.add(2);
        numbers.add(3);
        numbers.add(4);
        numbers.add(5);
        
        // 获取ArrayList的子列表
        List<Integer> subList = numbers.subList(1, 4);
        
        System.out.println("原始ArrayList中的元素：");
        for (Integer num : numbers) {
            System.out.print(num + " ");
        }
        System.out.println();
        
        System.out.println("子列表中的元素：");
        for (Integer num : subList) {
            System.out.print(num + " ");
        }
        System.out.println();
        
        // 修改子列表中的元素
        subList.set(0, 10);
        subList.set(1, 20);
        
        System.out.println("修改过后的原始ArrayList中的元素：");
        for (Integer num : numbers) {
            System.out.print(num + " ");
        }
        System.out.println();
    }
}

Run the above code, the output result is:

原始ArrayList中的元素：
1 2 3 4 5 
子列表中的元素：
2 3 4 
修改过后的原始ArrayList中的元素：
1 10 20 4 5 

As can be seen from the running results, through subList The sublist obtained by the () function has an impact on the original ArrayList. When we modify an element in the sublist, the corresponding element in the original ArrayList will also be modified.

It should be noted that the sublist returned by subList() cannot be added or deleted, otherwise an UnsupportedOperationException exception will be thrown.

As a result, the use of the ArrayList.subList() function allows the ArrayList data to be accurately valued according to a certain range, which facilitates subsequent operations. When using it, you need to pay attention to the range of the index and its impact on the original ArrayList in order to correctly obtain, modify and process elements in the sublist.

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