Java中抽象类的作用及说明

import java.sql.Connection;
 
/**
 * 数据库链接抽象类
 */
public abstract class AbstractDataBaseClass {
 
    /**
     * 注册驱动
     */
    public abstract void registerDriver();
 
    /**
     * 获取链接
     * @return
     */
    public abstract Connection getConnection();
 
    /**
     * 执行sql
     */
    public abstract void  executeSql();
 
    public void execute(){
        this.registerDriver();
        this.getConnection();
        this.executeSql();
    }
}

import java.sql.Connection;
 
/**
 * oracle具体实现类
 */
public class OracleDataBaseClass extends AbstractDataBaseClass {
    @Override
    public void registerDriver() {
        System.out.println("注册oracle数据驱动");
    }
 
    @Override
    public Connection getConnection() {
        System.out.println("获取oracle数据库链接");
        return null;
    }
 
    @Override
    public void executeSql() {
        System.out.println("在oracle数据库中执行sql");
    }
}

import java.sql.Connection;
 
/**
 * mysql具体实现类
 */
public class MysqlDataBaseClass extends AbstractDataBaseClass {
    @Override
    public void registerDriver() {
        System.out.println("注册mysql数据驱动");
    }
 
    @Override
    public Connection getConnection() {
        System.out.println("获取mysql数据库链接");
        return null;
    }
 
    @Override
    public void executeSql() {
        System.out.println("在mysql数据库中执行sql");
    }
}

public class DataBaseTest {
 
    public static void main(String[] args) {
        AbstractDataBaseClass mysql = new MysqlDataBaseClass();
        mysql.execute();
        System.out.println("----------------------------------------");
        AbstractDataBaseClass oracle = new OracleDataBaseClass();
        oracle.execute();
    }
}