java String i = [{"key":"value","key1":"value2"},{}]类型数据怎么转换成List格式

您好，可以使用Java中的Gson库来将JSON格式的字符串转换为List对象。

具体实现步骤如下：
1. 导入Gson库，可以在pom.xml文件中添加以下依赖：

<dependency>
    <groupId>com.google.code.gson</groupId>
    <artifactId>gson</artifactId>
    <version>2.8.7</version>
</dependency>

2. 使用Gson将JSON字符串转换为List对象，代码示例如下：

String jsonStr = "[{\"key\":\"value\",\"key1\":\"value2\"},{},{}]";
List<Map<String, String>> list = new Gson().fromJson(jsonStr, new TypeToken<List<Map<String, String>>>() {}.getType());

上述代码中，使用fromJson方法将JSON字符串转换为List对象，其中第一个参数为JSON字符串，第二个参数使用TypeToken指定转换的目标类型。

相关问题

Given a list of string, return a dictionary of key: value as string: number of times

To create a dictionary of key-value pairs where the key is a string from a list and the value is the number of times that string appears in the list, you can use a loop to iterate over the list and add each string to a dictionary with its count as the value. Here's an example code snippet:

def count_strings(lst):
    # create an empty dictionary
    string_counts = {}

    # iterate over the list
    for string in lst:
        # if the string is already in the dictionary, increment its count
        if string in string_counts:
            string_counts[string] += 1
        # otherwise, add the string to the dictionary with a count of 1
        else:
            string_counts[string] = 1

    # return the dictionary
    return string_counts

You can call this function with a list of strings as an argument to get a dictionary of string counts. For example:

count_strings(["apple", "banana", "apple", "orange", "banana", "pear"])

Output:

{'apple': 2, 'banana': 2, 'orange': 1, 'pear': 1}

java List<Map<String, String>>过滤掉部分key和对应的value

可以使用Java 8的流(Stream)来过滤List<Map<String, String>>中的key和对应的value。下面是一个示例代码：

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

public class Main {
    public static void main(String[] args) {
        List<Map<String, String>> list = new ArrayList<>();
        
        // 添加一些示例数据
        Map<String, String> map1 = new HashMap<>();
        map1.put("key1", "value1");
        map1.put("key2", "value2");
        map1.put("key3", "value3");
        list.add(map1);
        
        Map<String, String> map2 = new HashMap<>();
        map2.put("key1", "value1");
        map2.put("key2", "value2");
        map2.put("key3", "value3");
        list.add(map2);
        
        // 过滤掉部分key和对应的value
        List<Map<String, String>> filteredList = list.stream()
                .map(map -> {
                    // 创建一个新的Map，用于存放过滤后的数据
                    Map<String, String> filteredMap = new HashMap<>();
                    for (Map.Entry<String, String> entry : map.entrySet()) {
                        // 这里根据需要过滤的key进行判断
                        if (!entry.getKey().equals("key1") && !entry.getKey().equals("key3")) {
                            // 将符合条件的键值对添加到新的Map中
                            filteredMap.put(entry.getKey(), entry.getValue());
                        }
                    }
                    return filteredMap;
                })
                .collect(Collectors.toList());
        
        // 输出过滤后的结果
        for (Map<String, String> filteredMap : filteredList) {
            System.out.println(filteredMap);
        }
    }
}

输出结果为：

{key2=value2}
{key2=value2}