Tool class writing specification (for yourself)

Static utility class (*Util)
1. All constants are capitalized;
2. Declare the class as final to avoid inheritance;
3. Provide singleton mode;
4. Member methods do not need to be static;

for example:
package com.csc.jsoup;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

/**
*
* @author csc
*
*/
public final class DBUtil {

private static Connection conn = null;
private static Statement st = null;
private static ResultSet rs = null;

private DBUtil() {

}

private static final DBUtil instance = new DBUtil();

public static DBUtil getInstance() {
return instance;
}

/**
* 连接数据库
*
* @return
*/
public Connection connection() {
try {
Class.forName(Constants.DRIVER);
} catch (ClassNotFoundException e1) {
e1.printStackTrace();
}
try {
conn = DriverManager.getConnection(Constants.DBURL, Constants.USER,
Constants.PASSWORD);
} catch (SQLException e) {
e.printStackTrace();
}
return conn;
}

/**
* 关闭连接
*
* @param rs
* @param st
* @param conn
*/
public void release(ResultSet rs, Statement st, Connection conn) {
try {
try {
if (null != rs) {
rs.close();
}
} catch (Exception e) {
rs = null;
}
try {
if (null != st) {
st.close();
}
} catch (Exception e) {
st = null;
}
try {
if (null != conn) {
conn.close();
}
} catch (Exception e) {
conn = null;
}
} finally {
rs = null;
st = null;
conn = null;
}
}

/**
* 插入
* @param sql
*/
public void insert(String sql){
try{
DBUtil.getInstance().connection();
st = conn.createStatement();
st.execute(sql);
DBUtil.getInstance().release(rs, st, conn);
}catch(Exception e){
e.printStackTrace();
}
}




}