java代码大全及详解（java必背代码入门）

1. 字符串有整型的相互转换

Stringa = String.valueOf(2); //integer to numeric string

	





	int i = Integer.parseInt(a); //numeric string to an int

2. 向文件末尾添加内容

BufferedWriter out= ;

	





	try{



	out= newBufferedWriter(newFileWriter(”filename”, true));



	out.write(”aString”);



	} catch(IOException e) {



	// error processing code



	} finally{



	if(out!= ) {



	out.close();



	}



	}

3. 得到当前方法的名字

StringmethodName = Thread.currentThread().getStackTrace()[1].getMethodName();

4. 转字符串到日期

java.util.Date = java.text.DateFormat.getDateInstance().parse(dateString);

	





	或者是：



	SimpleDateFormat format= newSimpleDateFormat( "yyyy-MM-dd");



	Datedate= format.parse( myString );

5. 使用JDBC链接Oracle

publicclassOracleJdbcTest

	





	{



	String driverClass = "oracle.jdbc.driver.OracleDriver";



	Connection con;



	publicvoidinit(FileInputStream fs)throwsClassNotFoundException, SQLException, FileNotFoundException, IOException



	{



	Properties props = newProperties();



	props.load(fs);



	String url = props.getProperty("db.url");



	String userName = props.getProperty("db.user");



	String password = props.getProperty("db.password");



	Class.forName(driverClass);



	con=DriverManager.getConnection(url, userName, password);



	}



	publicvoidfetch()throwsSQLException, IOException



	{



	PreparedStatement ps = con.prepareStatement("select SYSDATE from dual");



	ResultSet rs = ps.executeQuery();



	while(rs.next())



	{



	// do the thing you do



	}



	rs.close();



	ps.close();



	}



	publicstaticvoidmain(String[] args)



	{



	OracleJdbcTest test = newOracleJdbcTest();



	test.init();



	test.fetch();



	}



	}

6.列出文件和目录

File dir = newFile("directoryName");

	





	String[] children = dir.list();



	if(children == ) {



	// Either dir does not exist or is not a directory



	} else{



	for(int i=0; i < children.length; i++) {



	// Get filename of file or directory



	Stringfilename = children[i];



	}



	}



	// It is also possible to filter the list of returned files.



	// This example does not return any files that start with `.'.



	FilenameFilter filter = newFilenameFilter() {



	publicbooleanaccept(File dir, Stringname) {



	return!name.startsWith(".");



	}



	};



	children = dir.list(filter);



	// The list of files can also be retrieved as File objects



	File[] files = dir.listFiles();



	// This filter only returns directories



	FileFilter fileFilter = newFileFilter() {



	publicbooleanaccept(File file) {



	returnfile.isDirectory();



	}



	};



	files = dir.listFiles(fileFilter);

7.解析/读取XML 文件

<?xml version="1.0"?>

	





	<students>



	<student>



	<name>John</name>



	<grade>B</grade>



	<age>12</age>



	</student>



	<student>



	<name>Mary</name>



	<grade>A</grade>



	<age>11</age>



	</student>



	<student>



	<name>Simon</name>



	<grade>A</grade>



	<age>18</age>



	</student>



	</students>

8. java分页代码实现

1publicclassPageBean{

	





	2privateintcurPage;//当前页



	3privateintpaount;//总页数



	4privateintrowsCount;//总行数



	5privateintpageSize=10;//每页多少行



	6



	7



	8



	9publicPageBean(introws){



	10



	11this.setRowsCount(rows);



	12if(this.rowsCount%this.pageSize==0){



	13this.paount=this.rowsCount/this.pageSize;



	14}



	15elseif(rows<this.pageSize){



	16this.paount=1;



	17}



	18else{



	19this.paount=this.rowsCount/this.pageSize+1;



	20}



	21}



	22



	23



	24publicintgetCurPage(){



	25returncurPage;



	26}



	27publicvoidsetCurPage(intcurPage){



	28this.curPage=curPage;



	29}



	30publicintgetPaount(){



	31returnpaount;



	32}



	33publicvoidsetPaount(intpaount){



	34this.paount=paount;



	35}



	36publicintgetPageSize(){



	37returnpageSize;



	38}



	39publicvoidsetPageSize(intpageSize){



	40this.pageSize=pageSize;



	41}



	42publicintgetRowsCount(){



	43returnrowsCount;



	44}



	45publicvoidsetRowsCount(introwsCount){



	46this.rowsCount=rowsCount;



	47}



	48}

分页展示如下

1Listclist=adminbiz.queryNotFullCourse();//将查询结果存放在List集合里

	





	2PageBeanpagebean=newPageBean(clist.size());//初始化PageBean对象



	3//设置当前页



	4pagebean.setCurPage(page);//这里page是从页面上获取的一个参数，页数



	5//获得分页大小



	6intpagesize=pagebean.getPageSize();



	7//获得分页数据在list集合中的索引



	8intfirstIndex=(page-1)*pagesize;



	9inttoIndex=page*pagesize;



	10if(toIndex>clist.size()){



	11toIndex=clist.size();



	12}



	13if(firstIndex>toIndex){



	14firstIndex=0;



	15pagebean.setCurPage(1);



	16}



	17//截取数据集合，获得分页数据



	18ListcourseList=clist.subList(firstIndex,toIndex);