import java.util.Properties;

/**
 * @author 一猿小讲
 */
public class JVMDetails {
    public static void main(String[] args) {
        // 获取系统信息（JDK信息、Java虚拟机信息、Java提供商信息、当前计算机用户信息）
        Properties properties = System.getProperties();
        // 把系统信息打印一下
        properties.list(System.out);
    }
}

import java.io.*;
import java.util.Hashtable;
import java.util.Properties;

/**
 * 配置文件工具类
 * 1. 支持加载 .properties文件、.ini文件
 * 2. 支持配置文件更新
 * @author 一猿小讲
 */
public class PropertiesUtil {

    // private static final Log4j LOG =  .....;

    private static Hashtable propCache = new Hashtable();

    public static String getString(String propFile, String key) {
        return getString(propFile, key, null);
    }

    public static String getString(String propFile, String key, String defaultValue) {
        if ((!propFile.endsWith(".properties")) && (!propFile.endsWith(".ini"))) {
            propFile = propFile + ".properties";
        }
        PropCache prop = propCache.get(propFile);
        if (prop == null) {
            try {
                prop = new PropCache(propFile);
            } catch (IOException e) {
                // LOG.warn(e);
                System.out.println(String.format("读取 %s 出现异常%s", propFile,e));
                return defaultValue;
            }
            propCache.put(propFile, prop);
        }
        String value = prop.getProperty(key, defaultValue);
        if (value != null) {
            value = value.trim();
        }
        return value;
    }

    public static void setString(String propFile, String key, String value)
            throws IOException {
        if ((!propFile.endsWith(".properties")) && (!propFile.endsWith(".ini"))) {
            propFile = propFile + ".properties";
        }
        File file = new File(propFile);
        Properties prop = new Properties();
        try {
            FileInputStream fis = new FileInputStream(file);
            prop.load(fis);
            fis.close();
        } catch (FileNotFoundException e) {
            // LOG.warn(e);
            System.out.println(String.format("文件 %s 不存在", propFile));
        }
        FileOutputStream fos = new FileOutputStream(file);
        prop.put(key, value);
        prop.store(fos, null);
        fos.close();
        PropCache localPropCache = propCache.get(propFile);
        if (localPropCache != null) {
            localPropCache.reload();
        }
    }

    private static class PropCache {

        private String fileName;
        private long lastLoad;
        private Properties prop;

        public PropCache(String propFileName) throws IOException {
            File file = new File(propFileName);
            FileInputStream fis = new FileInputStream(file);
            this.prop = new Properties();
            this.prop.load(fis);
            fis.close();
            this.fileName = file.getAbsolutePath();
            this.lastLoad = file.lastModified();
        }

        public String getProperty(String key, String defaultValue) {
            File file = new File(this.fileName);
            if (this.lastLoad 

/**
 * 测试类
 * @author 一猿小讲
 */
public class M {
    public static void main(String[] args) {
        while(true) {
            System.out.println(PropertiesUtil.getString("db", "jdbc.type"));
            try {
                Thread.sleep(10000);
            } catch (InterruptedException e) {
            }
        }
    }
}