java常用代码大全_编程常用代码

编程小6 Java (5) 2024-08-29 19:23

Hi，大家好，我是编程小6，很荣幸遇见你，我把这些年在开发过程中遇到的问题或想法写出来，今天说一说
java常用代码大全_编程常用代码,希望能够帮助你!!!。

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 = ;
try {
out = new BufferedWriter(new FileWriter(”filename”, true));
out.write(”aString”);
} catch (IOException e) {
// error processing code
} finally {
if (out != ) {
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 == ) {
// 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);