Java常用对象构造方法

Request:

HttpServletRequestrequest=ServletActionContext.getRequest();

Response:

HttpServletResponseresponse=ServletActionContext.getResponse();

Session(HttpSession):

HttpSession session= request.getSession();

application:

ServletContext application=pageContext. getServletContext();

Session(org.hibernate.Session):

Sessionsession=HibernateUtil.openSession();

Cookies：

Cookie[]cookies=request.getCookies();//通过请求获取到cookie

Out:

PrintWriterout=resp.getWriter();//(HttpServletResponse resp)

Context:

ServletContextcontext=req.getSession().getServletContext();

属性文件Properties:

Map<String,String> properties = new HashMap<String, String>();

系统属性Properties:

Properties properties=System.getProperties();

properties.list(System.out);  //打印系统属性

persons：泛型，只能保存一种类型

List<person> persons=newArrayList<person>();

Persons对象遍历：

for(person stu: persons){         System.out.println(stu.getPersonName());

}

List: 泛型，只能保存一种类型

List<String>list=new ArrayList<String>();

Set:

Set<Integer>set = new HashSet<Integer>();

arrayList:

ArrayList arrayList=new ArrayList();

hashMap:

HashMap hashMap=new HashMap();

hashSet:

HashSet hashSet=new HashSet();

linkedList:

LinkedList linkedList=new LinkedList();

键映射到值：

Map<Integer,student>students=new HashMap<Integer,student>();

请求转发:

RequestDispatcherrd=req.getRequestDispatcher("login.jsp");

rd.forward(req,resp);或者

req.getRequestDispatcher("index.jsp").forward(req,resp);

重定向：

resp.sendRedirect("login.jsp”);

转换成包装类：

int i=3;

Integer in=new Integer(i);

runtime：

Runtime runtime=Runtime.getRuntime();

Process p= runtime.exec("java Test");

InputStream is=p.getInputStream();

int data;

while((data=is.read())!=-1){

System.out.println((char)data);

}

线程：

Thread1 t1=new Thread1();

for循环遍历：

String[]a={"wo","men"};

for(String iii:a){

    System.out.println(iii);

}

迭代器:

Collection c;

Iterator it=c.iterator();

while(it.hasNext()){

    System.out.println(it.next());

}

字符流写入文件:

FileOutputStream fos=new FileOutputStream("test.txt");

OutputStreamWriter osw=new OutputStreamWriter(fos);

BufferedWriter bw=new BufferedWriter(osw);

bw.write("http://www.mybole.com.cn");

bw.close();

字符流读取文件:

FileInputStream fis=new FileInputStream("test.txt");

InputStreamReader isr=new InputStreamReader(fis);

BufferedReader br=new BufferedReader(isr);

System.out.println(br.readLine());//按行读取，只有一行，直接读取

br.close();

字节流到字符流的转换:

InputStreamReader isr2=new InputStreamReader(System.in);

BufferedReader br2=new BufferedReader(isr2);

String StrLine;

while((StrLine=br2.readLine())!=null){

System.out.println(StrLine);

}

br2.close();

写入字节流:

FileOutputStream fos=newFileOutputStream("1.txt");

fos.write("http://www.baidu.com".getBytes());

fos.close();//关闭*/

读取字节流:

FileInputStream fis=newFileInputStream("1.txt");

byte[] buf=new byte[100];

int len=fis.read(buf);

System.out.println(new String(buf,0,len));

fis.close();//关闭*/

文件创建:

File f1=new File("1.txt");//都是相对路径，在项目文件夹中产生

f1.createNewFile();     //创建一个新文件

f1.mkdir();//创建一个目录//也就是一个文件夹

得到当前Test类文件的所在目录:

URL url=Test.class.getResource("");

URI uri=null;

uri = url.toURI();

//例如file:/D:/java/studentJava/bin/util/   

//util为Test.java所在的包

获取源文件夹的文件或目录:

String path = "G:\\abc";

File[] file=new File(path).listFiles();