java代码大全及详解(精心整理Java语言常用代码汇总)

1. 字符串有整型的相互转换

String a = String.valueOf(2); //integer to numeric stringint i = Integer.parseInt(a); //numeric string to an int

1	String a = String.valueOf(2); //integer to numeric stringint 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;}}

1	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;

1	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 );

1	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 <strong>class</strong><strong>OracleJdbcTest</strong>{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;}<strong>public</strong><strong>static</strong><strong>void</strong><strong>main</strong>(String[] args){OracleJdbcTest test = new OracleJdbcTest;test.init;test.fetch;}}

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public <strong>class</strong><strong>OracleJdbcTest</strong>{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;}<strong>public</strong><strong>static</strong><strong>void</strong><strong>main</strong>(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 &lt; 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 objectsFile files = dir.listFiles;// This filter only returns directoriesFileFilter fileFilter = new FileFilter {public boolean accept(File file) {return file.isDirectory;}};files = dir.listFiles(fileFilter);

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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 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 objectsFile files = dir.listFiles;// This filter only returns directoriesFileFilter fileFilter = new FileFilter {public boolean accept(File file) {return file.isDirectory;}};files = dir.listFiles(fileFilter);

 

7.解析/读取XML 文件

&lt;?xml version="1.0"?&gt;&lt;students&gt;&lt;student&gt;&lt;name&gt;John&lt;/name&gt;&lt;grade&gt;B&lt;/grade&gt;&lt;age&gt;12&lt;/age&gt;&lt;/student&gt;&lt;student&gt;&lt;name&gt;Mary&lt;/name&gt;&lt;grade&gt;A&lt;/grade&gt;&lt;age&gt;11&lt;/age&gt;&lt;/student&gt;&lt;student&gt;&lt;name&gt;Simon&lt;/name&gt;&lt;grade&gt;A&lt;/grade&gt;&lt;age&gt;18&lt;/age&gt;&lt;/student&gt;&lt;/students&gt;

1

<?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6789<strong>public</strong><strong>PageBean</strong>(int rows){1011 this.setRowsCount(rows);12 if(this.rowsCount % this.pageSize == 0){13 this.pageCount=this.rowsCount / this.pageSize;14 }15 else if(rows&lt;this.pageSize){16 this.pageCount=1;17 }18 else{19 this.pageCount=this.rowsCount / this.pageSize +1;20 }21 }2223<strong>24 public</strong><strong>int</strong><strong>getCurPage</strong> {25 return curPage;26 }27<strong>public</strong><strong>void</strong><strong>setCurPage</strong>(int curPage) {28 this.curPage = curPage;29 }30<strong>public</strong><strong>int</strong><strong>getPageCount</strong> {31 return pageCount;32 }33<strong>public</strong><strong>void</strong><strong>setPageCount</strong>(int pageCount) {34 this.pageCount = pageCount;35 }36<strong>public</strong><strong>int</strong><strong>getPageSize</strong> {37 return pageSize;38 }39<strong>public</strong><strong>void</strong><strong>setPageSize</strong>(int pageSize) {40 this.pageSize = pageSize;41 }42<strong>public</strong><strong>int</strong><strong>getRowsCount</strong> {43 return rowsCount;44 }45<strong>public</strong><strong>void</strong><strong>setRowsCount</strong>(int rowsCount) {46 this.rowsCount = rowsCount;47 }48 }

1

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6789<strong>public</strong><strong>PageBean</strong>(int rows){1011 this.setRowsCount(rows);12 if(this.rowsCount % this.pageSize == 0){13 this.pageCount=this.rowsCount / this.pageSize;14 }15 else if(rows&lt;this.pageSize){16 this.pageCount=1;17 }18 else{19 this.pageCount=this.rowsCount / this.pageSize +1;20 }21 }2223<strong>24 public</strong><strong>int</strong><strong>getCurPage</strong> {25 return curPage;26 }27<strong>public</strong><strong>void</strong><strong>setCurPage</strong>(int curPage) {28 this.curPage = curPage;29 }30<strong>public</strong><strong>int</strong><strong>getPageCount</strong> {31 return pageCount;32 }33<strong>public</strong><strong>void</strong><strong>setPageCount</strong>(int pageCount) {34 this.pageCount = pageCount;35 }36<strong>public</strong><strong>int</strong><strong>getPageSize</strong> {37 return pageSize;38 }39<strong>public</strong><strong>void</strong><strong>setPageSize</strong>(int pageSize) {40 this.pageSize = pageSize;41 }42<strong>public</strong><strong>int</strong><strong>getRowsCount</strong> {43 return rowsCount;44 }45<strong>public</strong><strong>void</strong><strong>setRowsCount</strong>(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&gt;clist.size){11 toIndex=clist.size;12 }13 if(firstIndex&gt;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);

1

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);