Java 读写键值对

Properties类（读入写出 键值对） 是Map子类 Map方法都能用

 

public static void main(String[] args) throws IOException {

//读出

Properties pro=new Properties();

FileInputStream fis = new FileInputStream("F:\\Demo.properties");

//FileReader fr=new FileReader("F:\\Demo.properties");

pro.load(fis);//读取键值对 pro.load(fr);

String str=pro.getProperty("name");//取值

fis.close(); //fr.close();

 

//写入

Properties pro=new Properties();//创建集合

 

pro.setProperty("name","lisi");//写入键值对

pro.setProperty("hobby","eat");

pro.setProperty("hobby","sleep");//替换值

 

String str=pro.getProperty("name");//取值

Set<String> set=pro.stringPropertyNames();//像keySet获取 键值集合

for(String key:set){//遍历

System.out.println(key+"..."+pro.getProperty(key));

}

 

FileOutputStream fos=new FileOutputStream("F:\\aaa.properties",true);

//FileWriter fw = new FileWriter("F:\\aaa.properties",true);

 

pro.store(fos, "person information"); //(文件路径,添加理由)

//pro.store(fw,"save data");

fos.close();//5，关闭流

}

//父类方法：

Properties prop = new Properties();

prop.put("CZBK001", "zhangsan");//添加映射关系

 

Set<Object> keys = prop.keySet();

for (Object key : keys) {

Object value = prop.get(key);

System.out.println(key + "=" + value);

}

Set<Map.Entry<Object,Object>> entrys = prop.entrySet();

for (Map.Entry<Object, Object> entry : entrys) {

Object key = entry.getKey();

Object value = entry.getValue();

System.out.println(key + "=" + value);

}

 

PrintWriter pw = new PrintWriter("d.txt");//打印流对象

prop.list(pw);

pw.close();//释放资源

 

 

Properties类  JDBC从文件读取信息

 

public static Connection getConn(){

 

Connection conn=null; //不是局部

 

Properties pro=new Properties();

 

try{

 

FileInputStream fis=new FileInputStream("src/pro.properties");

 

pro.load(fis); //相对路径 正斜杠

 

Class.forName(pro.getProperty("driverClass"));//点出try catch

 

String url=pro.getProperty("url");

 

String username=pro.getProperty("username");

 

String password=pro.getProperty("password");//  空

 

conn=DriverManager.getConnection(url, username, password);//点 add catch

 

}

 

catch (ClassNotFoundException e) {e.printStackTrace();}

 

catch (SQLException e) {e.printStackTrace();}

 

catch (IOException e) {e.printStackTrace();}

 

return conn;

 

}

 

 

 

src/pro.properties文件：//无空格   密码空串（空格）

 

driverClass=com.mysql.jdbc.Driver

 

url=jdbc:mysql://localhost:3306/guanjiapo?useUnicode=true&characterEncoding=UTF-8&zeroDateTimeBehavior=convertToNull

 

username=root

 

password=