Java 常用代码汇总-附源码

快来打我* 2024-04-01 17:10 30阅读 0赞

**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 classOracleJdbcTest
    {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;
    }
    publicstaticvoidmain(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
    9publicPageBean(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 publicintgetCurPage {
    25 return curPage;
    26 }
    27publicvoidsetCurPage(int curPage) {
    28 this.curPage = curPage;
    29 }
    30publicintgetPageCount {
    31 return pageCount;
    32 }
    33publicvoidsetPageCount(int pageCount) {
    34 this.pageCount = pageCount;
    35 }
    36publicintgetPageSize {
    37 return pageSize;
    38 }
    39publicvoidsetPageSize(int pageSize) {
    40 this.pageSize = pageSize;
    41 }
    42publicintgetRowsCount {
    43 return rowsCount;
    44 }
    45publicvoidsetRowsCount(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);