Java新手入门常用代码大全，建议收藏并背会！

本文带大家了解Java新手入门的常用代码有哪些： 1. 字符串有整型的相互转换 String a = String.valueOf(2); //integer to numeric string int i = Integer.parseInt(a); //numeric strin...

本文带大家了解Java新手入门的常用代码有哪些：

1. 字符串有整型的相互转换

String a = 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 = null; try {   out = new BufferedWriter(new FileWriter(”filename”, true));   out.write(”aString”); } catch (IOException e) {   // error processing code } finally {   if (out != null) {     out.close();   } }

3. 得到当前方法的名字

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

4. 转字符串到日期

java.util.Date = java.text.DateFormat.getDateInstance().parse(date String);或者是：SimpleDateFormat format = new SimpleDateFormat( "yyyy-MM-dd" );  Date date = format.parse( myString );

5. 使用JDBC链接Oracle

public class OracleJdbcTest {   String driverClass = "oracle.jdbc.driver.OracleDriver";
  Connection con;
  public void init(FileInputStream fs) throws ClassNotFoundException, SQLException, FileNotFoundException, IOException {     Properties props = new Properties();     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);   }
  public void fetch() throws SQLException, 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();   }
  public static void main(String[] args) {     OracleJdbcTest test = new OracleJdbcTest();     test.init();     test.fetch();   } }

6.列出文件和目录

File dir = new File("directoryName");  String[] children = dir.list();  if (children == null) {    // 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      String filename = 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 = new FilenameFilter() {    public boolean accept(File dir, String name) {      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 = new FileFilter() {    public boolean accept(File file) {      return file.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

  public class PageBean {        private int curPage;             //当前页        private int pageCount;           //总页数        private int rowsCount;           //总行数        private int pageSize=10;         //每页多少行             public PageBean(int rows){           this.setRowsCount(rows);           if(this.rowsCount % this.pageSize == 0){               this.pageCount=this.rowsCount / this.pageSize;           }           else if(rows<this.pageSize){               this.pageCount=1;           }           else{               this.pageCount=this.rowsCount / this.pageSize +1;           }       }       public int getCurPage() {           return curPage;       }       public void setCurPage(int curPage) {           this.curPage = curPage;       }       public int getPageCount() {           return pageCount;       }       public void setPageCount(int pageCount) {           this.pageCount = pageCount;       }       public int getPageSize() {           return pageSize;       }       public void setPageSize(int pageSize) {           this.pageSize = pageSize;       }       public int getRowsCount() {           return rowsCount;       }       public void setRowsCount(int rowsCount) {           this.rowsCount = rowsCount;       }   }

分页展示如下

  List clist=adminbiz.queryNotFullCourse();//将查询结果存放在List集合里    PageBean pagebean=new PageBean(clist.size());//初始化PageBean对象    //设置当前页    pagebean.setCurPage(page); //这里page是从页面上获取的一个参数，代表页数    //获得分页大小    int pagesize=pagebean.getPageSize();    //获得分页数据在list集合中的索引    int firstIndex=(page-1)*pagesize;    int toIndex=page*pagesize;   if(toIndex>clist.size()){       toIndex=clist.size();   }   if(firstIndex>toIndex){       firstIndex=0;       pagebean.setCurPage(1);   }   //截取数据集合，获得分页数据   List courseList=clist.subList(firstIndex, toIndex);