Simple Java utility to manage jsons easily without extra libraries

JSON.java

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.HashMap;
import java.util.Map;

public class JSON {
    private Map<String, Object> map;
    private static String cached;
    
    private JSON() {
        this.map = new HashMap<>();
    }

    public Object get(String name) {
        return map.get(name);
    }

    public void put(String name, Object value) {
        map.put(name, value);
        cached = null;
    }
    
    public static JSON fromJsonFile(File file) throws IOException {
    	try (BufferedReader buf = new BufferedReader(new InputStreamReader(new FileInputStream(file)))) {
			StringBuilder builder = new StringBuilder();
			String line;
			
			while((line = buf.readLine()) != null) {
				builder.append(line);
			}
			
			return fromJsonString(builder.toString());
		}
    }
    
    public static JSON fromJsonString(String jsonString) {
        JSON json = new JSON();
        jsonString = jsonString.trim();

        if (jsonString.startsWith("{") && jsonString.endsWith("}")) {
            jsonString = jsonString.substring(1, jsonString.length() - 1).trim();
        }

        String[] keyValuePairs = jsonString.split(",(?=(?:[^\"]*\"[^\"]*\")*[^\"]*$)");

        for (String pair : keyValuePairs) {
            String[] entry = pair.split(":", 2);
            String key = entry[0].trim().replaceAll("^\"|\"$", "");
            String value = entry[1].trim();

            if (value.startsWith("\"") && value.endsWith("\"")) {
                json.put(key, value.substring(1, value.length() - 1));
            } else if ("true".equals(value) || "false".equals(value)) {
                json.put(key, Boolean.parseBoolean(value));
            } else if ("null".equals(value)) {
                json.put(key, null);
            } else {
                try {
                    json.put(key, value.contains(".") ? Double.parseDouble(value) : Integer.parseInt(value));
                } catch (NumberFormatException e) {
                    json.put(key, value);
                }
            }
        }
        
        cached = json.toString();
        return json;
    }
    
    private String formatValue(Object value) {
        if (value instanceof String) {
            return "\"" + value + "\"";
        }
        if (value instanceof JSON) {
            return value.toString();
        }
        return String.valueOf(value);
    }
    
    @Override
    public String toString() {
    	if(cached == null) {
            StringBuilder json = new StringBuilder();
            json.append("{");

            int count = 0;
            for (Map.Entry<String, Object> entry : map.entrySet()) {
                json.append("\"").append(entry.getKey()).append("\": ");
                json.append(formatValue(entry.getValue()));

                count++;
                if (count < map.size()) {
                    json.append(", ");
                }
            }

            json.append("}");
            cached = json.toString();
    	}
    	
    	return cached;
    }
}