Question

我想把java中的局部变量的返回值返回出来

package com.test;

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

public class conmysql {

public static void consql(String s,String col){
String cost;
try {
Class.forName("com.mysql.jdbc.Driver");

} catch (ClassNotFoundException e1) {
e1.printStackTrace();
}
//链接数据库
try {
Connection con=DriverManager.getConnection("jdbc:mysql://192.168.1.250:3306/shop","fmrom","fmrom");
if(!con.isClosed()){
Statement st=con.createStatement();
ResultSet rs=st.executeQuery(s);
while(rs.next()){
cost = rs.getString(col);
System.out.print("数据库中的价格："+cost+" ");
}
}
con.close();
} catch (SQLException e) {
e.printStackTrace();
}

}

}
我想把cost的值return出来，并且在其他的类中还能调用consql(String s,String col)这个方法，改怎么做啊

Answer 1

package com.test;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.List;

public class conmysql {
	// 加个静态的返回值字段
    private List<String> recost;
    

	public List<String> getRecost() {
		return recost;
	}


	public void setRecost(List<String> recost) {
		conmysql.recost = recost;
	}


	public void consql(String s,String col){
         String cost; 
         recost = new ArrayList<String>();
        try {
            Class.forName("com.mysql.jdbc.Driver");
            
        } catch (ClassNotFoundException e1) {
            e1.printStackTrace();
        }
        //链接数据库
        try {
            Connection con=DriverManager.getConnection("jdbc:mysql://192.168.1.250:3306/shop","fmrom","fmrom");
            if(!con.isClosed()){
                Statement st=con.createStatement();
                ResultSet rs=st.executeQuery(s);
                while(rs.next()){
                    cost = rs.getString(col);
                    // 将cost放入集合recost;
                    recost.add(cost);
                    System.out.print("数据库中的价格："+cost+"    ");                
                }
            }
            con.close();            
        } catch (SQLException e) {
            e.printStackTrace();
        }        
        
    }
    
}

通过new conmysql().getRecost()可以拿到结果cost的集合,这样可以吗?

Answer 2

public class conmysql {
private String cost;

public String getCost(){
return cost;
}

public void consql(String s,String col){
try {
Class.forName("com.mysql.jdbc.Driver");

} catch (ClassNotFoundException e1) {
e1.printStackTrace();
}
//链接数据库
try {
Connection con=DriverManager.getConnection("jdbc:mysql://192.168.1.250:3306/shop","fmrom","fmrom");
if(!con.isClosed()){
Statement st=con.createStatement();
ResultSet rs=st.executeQuery(s);
while(rs.next()){
cost = rs.getString(col);
System.out.print("数据库中的价格："+cost+" ");
}
}
con.close();
} catch (SQLException e) {
e.printStackTrace();
}

}

}

其他地方调用：
conmysql myCon = new conmysql();
myCon:consql(str, col)
string myCost = myCon:getCost()
希望能帮到你

Answer 3

改方法返回类型，最后一行加上return cost；
public static String consql(String s,String col){

....

return cost;
}

Answer 4

public String consql(String s,String col){//static去掉

String cost;

(这里是你写的代码)

catch了Exception后面 return cost；
}

使用这个方法就：conmysql c=new conmysql();
c.consql(String s,String col);