如何实现 删除新闻分类，若是分类下有新闻，就不能删除，若是无新闻信息，就可以删除？

 BaseDao.java

package com.kgc.dao;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.sql.DataSource;

import com.kgc.util.ConfigManager;

public class BaseDao {
	//实现增删改查的功能  以及连接 和释放资源
	Connection cnt=null;
	PreparedStatement ps=null;
	ResultSet rs=null;
	
	
	public boolean getConnection(){
		String driver="com.mysql.jdbc.Driver";
		String url="jdbc:mysql://localhost:3306/kgcnews";
		String username="root";
		String password="root";
		try {
			Class.forName(driver);
			cnt=DriverManager.getConnection(url,username,password);
			
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return true;
		
		
	}
	
	//关闭资源
	public boolean closeResource(){
		if(rs!=null){
			try {
				rs.close();
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		
		if(ps!=null){
			try {
				ps.close();
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		
		if(cnt!=null){
			try {
				cnt.close();
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		return true;
		
	}
	
	//增删改
	public int executeUpdate(String sql ,Object [] params){
		int updateRows=0;
		if(this.getConnection()){
			//获得sql语句
			try {
				ps=cnt.prepareStatement(sql);
				//给占位符的赋值
				for(int i=0;i

package com.kgc.dao;

import com.kgc.pojo.NewsCategory;

public interface NewsCategoryDao {
	//删除
	public boolean deleteNewsCategoryById(NewsCategory nc);
}

package com.kgc.dao;

import java.util.Date;

import com.kgc.pojo.News;
import com.kgc.pojo.NewsCategory;
   //接口类
public interface NewsDao {
	//查询全部信息
	public void getList();
	
	//查询部分信息
	public void getNewsTitle(News news);
	
	//增
	public void add(News news);
	//public void add(int id,int categoryId,String title,
			//String summary,String content,Date createDate);
	//删
	public void delete(News news);
	//改
	public void update(News news);
	//统计 新闻分类被使用次数
	public int getCountCategoryIdByNewsDetail(NewsCategory nc);
	
}

package com.kgc.dao.impl;

import com.kgc.dao.BaseDao;
import com.kgc.dao.NewsCategoryDao;
import com.kgc.pojo.NewsCategory;

public class NewsCategoryDaoImpl extends BaseDao implements NewsCategoryDao {
	
	//删除
	@Override
	public boolean deleteNewsCategoryById(NewsCategory nc) {
		// TODO Auto-generated method stub
		String sql="delete from news_category where id=?";
		Object [] params={nc.getId()};
		if(this.getConnection()){
			int i=this.executeUpdate(sql, params);
			if(i>0){
				System.out.println("删除成功");
			}
			
		}
			this.closeResource();
		
		return true;
	}

}

package com.kgc.dao.impl;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Timestamp;
import java.util.Date;

import com.kgc.dao.BaseDao;
import com.kgc.dao.NewsDao;
import com.kgc.pojo.News;
import com.kgc.pojo.NewsCategory;

public class NewsDaoImpl extends BaseDao implements NewsDao{
	ResultSet rs=null;
	Connection cnt=null;
	PreparedStatement ps=null;
	
	//查询全部信息
	@Override
	public void getList() {
		// TODO Auto-generated method stub
		String sql="select id, categoryId,title,summary, content,picPath,author,createDate,modifyDate from news_detail";
		//初始化 数组 ，避免空指针
		Object[] params={};
		rs=this.ExecuteQuery(sql, params);
		//在控制台输出 rs的结果集
		try {
			while(rs.next()){
				int id=rs.getInt(1);
				int categoryId=rs.getInt(2);
				String title=rs.getString("title");
				String summary=rs.getString(4);
				String content=rs.getString(5);
				String picPath=rs.getString(6);
				String author=rs.getString(7);
				Date createDate=rs.getDate(8);
				Date modifyDate=rs.getDate(9);
				System.out.println(id+"\t"+categoryId+"\t"+title+"\t"+summary+"\t"+content+"\t"+picPath+"\t"+author+"\t"+createDate+"\t"+modifyDate );
			}
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally{
			this.closeResource();
		}
		
	}
	
//查询部分信息
	@Override
	public void getNewsTitle(News news) {
		// TODO Auto-generated method stub
		//返回值是ResultSet类型
		String sql="select id, categoryId,title,summary, content,picPath,author,createDate,modifyDate from news_detail where title like ?";
		Object [] params={news.getTitle()};
		rs=this.ExecuteQuery(sql, params);
		//在控制台遍历出 结果集
		try {
			while(rs.next()){
				int id=rs.getInt(1);
				int categoryId=rs.getInt(2);
				String title1=rs.getString("title");
				String summary=rs.getString(4);
				String content=rs.getString(5);
				String picPath=rs.getString(6);
				String author=rs.getString(7);
				Date createDate=rs.getDate(8);
				Date modifyDate=rs.getDate(9);
				System.out.println(id+"\t"+categoryId+"\t"+title1+"\t"+summary+"\t"+content+"\t"+picPath+"\t"+author+"\t"+createDate+"\t"+modifyDate );
			}
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally{
			this.closeResource();
		}
	}

	//增
	@Override
	public void add(News news) {
		// TODO Auto-generated method stub
		String sql="insert into news_detail(id,  categoryId,  title,  summary,content,  createDate) values(?,?,?,?,?,?)";
		//Object [] params={id,  categoryId,  title,  summary,content,  createDate};
		Object[] params={news.getId(),news.getCategoryId(),news.getTitle(),news.getSummary()
				,news.getContent(),news.getCreateDate()};
		int i=this.executeUpdate(sql, params);
		if(i>0){
			System.out.println("添加成功");
		}
	}

	//删除
	@Override
	public void delete(News news) {
		// TODO Auto-generated method stub
		String sql="delete from news_detail where id=?";
		Object [] params={news.getId()};
		int i=this.executeUpdate(sql, params);
		if(i>0){
			System.out.println("删除成功");
		}
	}
	
//修改
	@Override
	public void update(News news) {
		// TODO Auto-generated method stub
		String sql="update news_detail set title=? where id=?";
		Object [] params={news.getTitle(),news.getId()};
		int i=this.executeUpdate(sql, params);
		if(i>0){
			System.out.println("修改成功");
			
		}
	}
	

	
	//统计 新闻分类被使用次数
	@Override
	public int getCountCategoryIdByNewsDetail(NewsCategory nc) {
		// TODO Auto-generated method stub
		int i=0;
		String sql="SELECT COUNT(*)  FROM news_detail WHERE categoryId=?";
		Object [] params={nc.getId()};
		if(this.getConnection()){
			rs=this.ExecuteQuery(sql, params);
			try {
				while(rs.next()){
					i=rs.getInt(1);
				}
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}finally{
				this.closeResource();
			}
		}
		return i;
	}

}

package com.kgc.pojo;

import java.util.Date;

public class News {
	private int id;
	private int categoryId;
	private String title;
	private String summary;
	private String content;
	private String picPath;
	private String author;
	private Date createDate;
	
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	
	public int getCategoryId() {
		return categoryId;
	}
	public void setCategoryId(int categoryId) {
		this.categoryId = categoryId;
	}
	
	public String getTitle() {
		return title;
	}
	public void setTitle(String title) {
		this.title = title;
	}
	
	public String getSummary() {
		return summary;
	}
	public void setSummary(String summary) {
		this.summary = summary;
	}
	
	public String getContent() {
		return content;
	}
	public void setContent(String content) {
		this.content = content;
	}
	
	public String getPicPath() {
		return picPath;
	}
	public void setPicPath(String picPath) {
		this.picPath = picPath;
	}
	
	public String getAuthor() {
		return author;
	}
	public void setAuthor(String author) {
		this.author = author;
	}
	
	public Date getCreateDate() {
		return createDate;
	}
	public void setCreateDate(Date createDate) {
		this.createDate = createDate;
	}
	
	
}

package com.kgc.pojo;

import java.util.Date;

public class NewsCategory {
	private int id;
	private String name;
	private Date createDate;
	
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public Date getCreateDate() {
		return createDate;
	}
	public void setCreateDate(Date createDate) {
		this.createDate = createDate;
	}
	
	
}

package com.kgc.service;

import com.kgc.pojo.NewsCategory;

public interface NewsCategoryService {
	//根据新闻信息是否存在该分类决定是否删除该分类
	public boolean deleteNewsCategoryById(NewsCategory nc);
}

package com.kgc.service.impl;

import com.kgc.dao.NewsCategoryDao;
import com.kgc.dao.NewsDao;
import com.kgc.dao.impl.NewsCategoryDaoImpl;
import com.kgc.dao.impl.NewsDaoImpl;
import com.kgc.pojo.NewsCategory;
import com.kgc.service.NewsCategoryService;

public class NewsCategoryServiceImpl implements NewsCategoryService {
	NewsCategoryDao ncd=new NewsCategoryDaoImpl();
	NewsDao nd=new NewsDaoImpl();
	
	//根据新闻信息是否存在该分类决定是否删除该分类
	public boolean deleteNewsCategoryById(NewsCategory nc){
		//判断这个分类是否被使用，如果使用了，就不能删除，若是没有被使用，可以直接删除
		
		int i=nd.getCountCategoryIdByNewsDetail(nc);
		if(i>0){
			System.out.println("该分类不能删除");
		}else{
			//执行删除
			ncd.deleteNewsCategoryById(nc);
			System.out.println("删除成功");
		}
		return false;
		
	}

}

package com.kgc.service.impl;

import com.kgc.pojo.NewsCategory;
import com.kgc.service.NewsCategoryService;

public class Test {
	public static void main(String[] args) {
		
		NewsCategoryService ncs=new NewsCategoryServiceImpl();
		NewsCategory nc=new NewsCategory();
		nc.setId(6);
		ncs.deleteNewsCategoryById(nc);
		
	}
}