一、Hashmap和Hashtable的区别
1 主要:Hashtable线程安全,同步,效率相对低下
HashMap线程不安全,非同步,效率相对高
2 父类:Hashtable是Dictionary HashMap是AbstractMap
3 rull:Hashtable键与值不能为null
HashMap键最多一个null,值可心多个null
二 Property
1 作用:读写资源配置文件
2 键与值只能为字符串
3 方法:
setProperty(String key,String value)
getProperty(String key)
getProperty(String key,String defaultValue)
后缀:properties
store(OutputStream out,String coomments)
store(Writer writer,String coomments)
load(inputStream instream)
load(Reader reader)
.xml
storeToXml(OutputStream os,String coomments):UTF-8字符集
storeToXml(OutputStream os,String coomments,String encoding)
loadFromXML(inputStream in)
/*运用Properties输出到文件*/
public static void main(String[] args) throws FileNotFoundException, IOException {
//创建对象
Properties properties=new Properties();
//存储
properties.setProperty("driver", "oracle.jdbc.driver.OracleDriver");
//存储到e:/others绝对路径
properties.store(new FileOutputStream(new File("e:/others/db.properties")), "db配置");
properties.storeToXML(new FileOutputStream(new File("e:/others/db.xml")), "db配置");
properties.load(new FileReader("e:/others/db.properties"));
System.out.println(properties.getProperty("user","Lili"));