使ArrayList元素不区分大小写

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

public class CaseInsensitiveArrayList<T> extends ArrayList<T> {
    @Override
    public boolean contains(Object o) {
        String element = o.toString().toLowerCase();
        for (T item : this) {
            if (item.toString().toLowerCase().equals(element)) {
                return true;
            }
        }
        return false;
    }

    @Override
    public boolean add(T t) {
        String element = t.toString().toLowerCase();
        for (T item : this) {
            if (item.toString().toLowerCase().equals(element)) {
                return false;
            }
        }
        return super.add(t);
    }

    @Override
    public void add(int index, T element) {
        String newElement = element.toString().toLowerCase();
        for (T item : this) {
            if (item.toString().toLowerCase().equals(newElement)) {
                return;
            }
        }
        super.add(index, element);
    }

    @Override
    public boolean remove(Object o) {
        String element = o.toString().toLowerCase();
        for (T item : this) {
            if (item.toString().toLowerCase().equals(element)) {
                return super.remove(item);
            }
        }
        return false;
    }

    @Override
    public T remove(int index) {
        return super.remove(index);
    }

    @Override
    public void sort(Comparator<? super T> c) {
        super.sort(c);
    }
}

CaseInsensitiveArrayList<String> list = new CaseInsensitiveArrayList<>();
list.add("Apple");
list.add("banana");
list.add("Orange");

System.out.println(list.contains("apple")); // 输出：true
System.out.println(list.contains("BANANA")); // 输出：true
System.out.println(list.contains("orange")); // 输出：true
System.out.println(list.contains("grape")); // 输出：false

list.remove("APPLE");
System.out.println(list.contains("apple")); // 输出：false