Java 常用代码汇总

Java 常用代码汇总

1.Java 常用代码汇总

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);

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);