如何移除POJO集合中所有id等于指定值的元素？

Hey there! Let's work through this problem together. First off, I notice the sample data from your server isn't valid JSON for a collection of Item objects—right now it's a single object with duplicate keys, which isn't what you need. A valid JSON array for your Item collection should look like this:

[
    {"id":2,"name":"Ali"},
    {"id":3,"name":"janice"},
    {"id":2,"name":"Ali"},
    {"id":5,"name":"tupac"},
    {"id":2,"name":"Ali"},
    {"id":8,"name":"William"},
    {"id":2,"name":"Ali"}
]

First, make sure you parse this valid JSON into a List<Item> using a library like Jackson or Gson. For example, with Jackson:

ObjectMapper objectMapper = new ObjectMapper();
List<Item> originalItems = objectMapper.readValue(yourJsonString, new TypeReference<List<Item>>() {});

Now, let's cover a few straightforward ways to batch remove all items where id == 2:

1. Java 8+ Stream API (Clean & Concise) #

This is my go-to for readability. We'll create a new filtered collection without modifying the original:

import java.util.stream.Collectors;

List<Item> filteredItems = originalItems.stream()
    .filter(item -> item.getId() != 2) // Keep items where id is NOT 2
    .collect(Collectors.toList());

2. Iterator (Modify Original Collection) #

If you need to remove elements directly from the original list (instead of creating a new one), use an Iterator to avoid ConcurrentModificationException (which happens if you try to remove items with a regular for-loop):

import java.util.Iterator;

Iterator<Item> iterator = originalItems.iterator();
while (iterator.hasNext()) {
    Item currentItem = iterator.next();
    if (currentItem.getId() == 2) {
        iterator.remove(); // Safely remove the element
    }
}

3. Using Guava (Optional, for Utility Lovers) #

If you're using the Guava library, you can use Collections2.filter to create a filtered view, then convert it to a list if needed:

import com.google.common.collect.Collections2;

// Creates a filtered view (changes to original list affect this view)
Collection<Item> filteredView = Collections2.filter(originalItems, item -> item.getId() != 2);
// If you want an independent list:
List<Item> filteredList = new ArrayList<>(filteredView);

All these methods will leave you with only the items where id is 3, 5, or 8—exactly what you need!

内容的提问来源于stack exchange，提问作者ken