使用Getters时返回不可修改的列表

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

public class Example {
    private List<String> internalList = new ArrayList<>();

    public Example() {
        internalList.add("Item1");
        internalList.add("Item2");
    }

    public List<String> getUnmodifiableList() {
        return Collections.unmodifiableList(internalList);
    }

    public static void main(String[] args) {
        Example example = new Example();
        List<String> list = example.getUnmodifiableList();
        // 尝试修改列表会抛出 UnsupportedOperationException
        // list.add("Item3"); // 这行代码会抛出异常
    }
}

import com.google.common.collect.ImmutableList;

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

public class Example {
    private List<String> internalList = new ArrayList<>();

    public Example() {
        internalList.add("Item1");
        internalList.add("Item2");
    }

    public ImmutableList<String> getUnmodifiableList() {
        return ImmutableList.copyOf(internalList);
    }

    public static void main(String[] args) {
        Example example = new Example();
        ImmutableList<String> list = example.getUnmodifiableList();
        // 尝试修改列表会抛出 UnsupportedOperationException
        // list.add("Item3"); // 这行代码会抛出异常
    }
}

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

public class Example {
    private List<String> internalList = new ArrayList<>();

    public Example() {
        internalList.add("Item1");
        internalList.add("Item2");
    }

    public List<String> getUnmodifiableList() {
        return Collections.unmodifiableList(new ArrayList<>(internalList));
    }

    public static void main(String[] args) {
        Example example = new Example();
        List<String> list = example.getUnmodifiableList();
        // 即使修改原始列表，返回的不可修改列表也不会受到影响
        example.internalList.add("Item3");
        System.out.println(list); // 输出: [Item1, Item2]
    }
}