1. 字串有整型的相互轉換

String a = String.valueOf(2);   //integer to numeric string  
int i = Integer.parseInt(a); //numeric string to an int

2. 向檔案末尾新增內容

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. 得到當前方法的名字

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

4. 轉字串到日期

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連結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.列出檔案和目錄

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/讀取XML 檔案

<?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分頁程式碼實現

 1 public class PageBean {  
 2     private int curPage;             //當前頁  
 3     private int pageCount;           //總頁數  
 4     private int rowsCount;           //總行數  
 5     private int pageSize=10;         //每頁多少行  
 6       
 7       
 8       
 9     public PageBean(int rows){  
10           
11         this.setRowsCount(rows);  
12         if(this.rowsCount % this.pageSize == 0){  
13             this.pageCount=this.rowsCount / this.pageSize;  
14         }  
15         else if(rows<this.pageSize){  
16             this.pageCount=1;  
17         }  
18         else{  
19             this.pageCount=this.rowsCount / this.pageSize +1;  
20         }  
21     }  
22       
23       
24     public int getCurPage() {  
25         return curPage;  
26     }  
27     public void setCurPage(int curPage) {  
28         this.curPage = curPage;  
29     }  
30     public int getPageCount() {  
31         return pageCount;  
32     }  
33     public void setPageCount(int pageCount) {  
34         this.pageCount = pageCount;  
35     }  
36     public int getPageSize() {  
37         return pageSize;  
38     }  
39     public void setPageSize(int pageSize) {  
40         this.pageSize = pageSize;  
41     }  
42     public int getRowsCount() {  
43         return rowsCount;  
44     }  
45     public void setRowsCount(int rowsCount) {  
46         this.rowsCount = rowsCount;  
47     }  
48 }  

分頁展示如下

 1 List clist=adminbiz.queryNotFullCourse();//將查詢結果存放在List集合裡  
 2 PageBean pagebean=new PageBean(clist.size());//初始化PageBean物件  
 3 //設定當前頁  
 4 pagebean.setCurPage(page); //這裡page是從頁面上獲取的一個引數，代表頁數  
 5 //獲得分頁大小  
 6 int pagesize=pagebean.getPageSize();  
 7 //獲得分頁資料在list集合中的索引  
 8 int firstIndex=(page-1)*pagesize;  
 9 int toIndex=page*pagesize;  
10 if(toIndex>clist.size()){  
11     toIndex=clist.size();  
12 }  
13 if(firstIndex>toIndex){  
14     firstIndex=0;  
15     pagebean.setCurPage(1);  
16 }  
17 //擷取資料集合，獲得分頁資料  
18 List courseList=clist.subList(firstIndex, toIndex);