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Java常用代码汇总

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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

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<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);