Summary of commonly used code in Java

1. Strings can be converted to and from integers

String a = String.valueOf(2); //integer to numeric string
int i = Integer.parseInt(a); //numeric string to an int
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2. Add content to the end of the file

BufferedWriter out = null;
try {
  out = new BufferedWriter(newFileWriter (" filename ",true)); AString out. Write (" "); }catch (IOException e) {
  // error processing code
} finally {
  if(out ! =null) { out.close(); }}Copy the code

3. Get the name of the current method

String methodName = Thread.currentThread().getStackTrace()[1].getMethodName();
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4. Roll the string to the date

java.util.Date = java.text.DateFormat.getDateInstance().parse(date String); Or: SimpleDateFormat format =new SimpleDateFormat( "yyyy-MM-dd" );
Date date = format.parse( myString );
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5. Use JDBC to connect to 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(a) 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 = newOracleJdbcTest(); test.init(); test.fetch(); }}Copy the code

6. List files and directories

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 directoryString 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) {
     returnfile.isDirectory(); }}; files = dir.listFiles(fileFilter);Copy the code

7. Parse/read XML files

      
<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>West Gate</name>
<grade>A</grade>
<age>18</age>
</student>
</students>
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Java paging code implementation

 public class PageBean {  
     private int curPage;     / / the current page
     private int pageCount;   / / the total number of pages
     private int rowsCount;   / / the total number of rows
     private int pageSize=10; // How many lines per page
   
     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(a) {
         return curPage;
     }
     public void setCurPage(int curPage) {
         this.curPage = curPage;
     }
     public int getPageCount(a) {
         return pageCount;
     }
     public void setPageCount(int pageCount) {
         this.pageCount = pageCount;
     }
     public int getPageSize(a) {
         return pageSize;
     }
     public void setPageSize(int pageSize) {
         this.pageSize = pageSize;
     }
     public int getRowsCount(a) {
         return rowsCount;
     }
     public void setRowsCount(int rowsCount) {
         this.rowsCount = rowsCount; }}Copy the code

Page display as follows

  List clist = adminbiz.queryNotFullCourse();// Store the query result in the List collection
  PageBean pagebean = new PageBean(clist.size());// Initialize the PageBean object
  // Set the current page
  pagebean.setCurPage(page); // Here page is a parameter from the page, representing the number of pages
  // Get the page size
  int pagesize = pagebean.getPageSize();
  // Get the index of paging data in the list collection
  int firstIndex = (page - 1) * pagesize;
  int toIndex = page * pagesize;
  if (toIndex > clist.size()) {
     toIndex = clist.size();
  }
  if (firstIndex > toIndex) {
      firstIndex = 0;
      pagebean.setCurPage(1);
  }
  // Select paged data from paged data
  List courseList = clist.subList(firstIndex, toIndex);
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