Java常用代码汇总(经典代码)

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

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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(); 
  } 
}

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3. 得到当前方法的名字

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

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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 );

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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(); 
  } 
}

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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

 
 
   
    John 
    B 
    12 
   
   
    Mary 
    A 
    11 
   
   
    Simon 
    A 
    18 
   

8.java分页代码实现

 1 public class PageBean {  
 2     private int curPage;             //当前页  
 3     private int pageCount;           //总页数  
 4     private int rowsCount;           //总行数  
 5     private int pageSize=10;         //每页多少行  
 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

分页展示如下

 1 List clist=adminbiz.queryNotFullCourse();//将查询结果存放在List集合里  
 2 PageBean pagebean=new PageBean(clist.size());//初始化PageBean对象  
 3 //设置当前页  
 4 pagebean.setCurPage(page); //这里page是从页面上获取的一个参数，代表页数  
 5 //获得分页大小  
 6 int pagesize=pagebean.getPageSize();  
 7 //获得分页数据在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 //截取数据集合，获得分页数据  
18 List courseList=clist.subList(firstIndex, toIndex);