如何为Java集合创建一个mutable.Builder？

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

public class MyCollection {
    private List<String> items;

    private MyCollection(Builder builder) {
        this.items = builder.items;
    }

    public List<String> getItems() {
        return items;
    }

    public static class Builder {
        private List<String> items;

        public Builder() {
            this.items = new ArrayList<>();
        }

        public Builder addItem(String item) {
            this.items.add(item);
            return this;
        }

        public Builder addItems(List<String> items) {
            this.items.addAll(items);
            return this;
        }

        public MyCollection build() {
            return new MyCollection(this);
        }
    }
}

MyCollection collection = new MyCollection.Builder()
        .addItem("Item 1")
        .addItem("Item 2")
        .addItems(Arrays.asList("Item 3", "Item 4"))
        .build();

List<String> items = collection.getItems();
System.out.println(items);  // 输出: [Item 1, Item 2, Item 3, Item 4]