如何把ArrayList的数据从一类迁移到另一个类 [英] How to migrate the data of my arraylist from one class to another class

问题描述

所以，我有我的 ERDBUILDER.java 类是拉丝面板，让我画存储一个ArrayList 连接<内部形状/ code>。我也喜欢基于ArrayList中从另一个类SQL.java访问此ArrayList和创建我的SQL语句。我已经试过codeS后面，但我不知道主类应该如何。我试图把新的SQL（）; 主类，但它打开另一个 ERDBUILDER.java 类和这不正是我想要做的事。
那么，如何可以运行此，主类应该如何？

EDITED
任何人都可以帮忙吗？

\r

\r

包项目;\r
进口java.awt.Shape中;\r
进口的java.util.ArrayList;\r
进口project.ERDBUILDER.DrawingBoard.Attribute;\r
进口project.ERDBUILDER.DrawingBoard.Connection;\r
进口project.ERDBUILDER.DrawingBoard.Connection2;\r
进口project.ERDBUILDER.DrawingBoard.NamedShape;\r
\r
\r
公共类SQL {\r
\r
公共静态无效的主要（字符串ARGS []）{\r
       ArrayList的＆LT;连接GT＆; CON =新的ArrayList＆LT;＆GT;（）;\r
       \r
        对于（int类型的= 0; A＆LT; con.size（）; A ++）{\r
                                    NamedShape F = con.get（一）.getNamedShape1（）;\r
                                    属性G = con.get（一）.getNamedShape2（）;\r
                                    串I = f.getName（）;\r
                                    串J = g.getName（）;\r
\r
                                    形状Y = f.getShape（）;\r
                                    形状Y1 = g.getShape（）;\r
                                    的System.out.println第（i +和+ J +链接）;\r
                                    \r
                                    \r
                                    \r
                                   \r
        }\r
   }\r
   \r
}

\r

\r

\r

解决方案

要在其中创建SQL语句和连接的ArrayList传递给类，创建类的实例。

 列表＆LT;连接GT＆; CON =新的ArrayList＆LT;＆GT;（）;
ERDBuilder X =新ERDBuilder（CON）;
 

您ERDBuilder构造可以采取一个List对象，并用它来建立一个SQL语句。或者，你甚至可以做到这一点的ERDBuilder的方法。这是你的选择。

  ERDBuilder X =新ERDBuilder（）;
清单＆LT;连接GT＆; CON =新的ArrayList＆LT;＆GT;（）;
x.buildSql（CON）;
 

如果您想从主做它，那么你必须声明的列表作为类级别的变量，你已经在做ERDBuilder以同样的方式。

So i have my an ERDBUILDER.java class is a drawing panel which allows me to draw shapes that are stored inside an arraylist Connection. I would liked to access this arraylist from another class SQL.java and create my sql statement based on the arraylist. I've tried the codes that follows but i don't know how the main class should be. I've tried to put new SQL(); in the main class but it's opening another ERDBUILDER.java class and that not what i want it to do. So how can i run this, how the main class should be?

EDITED Anyone can help?

package project;
import java.awt.Shape;
import java.util.ArrayList;
import project.ERDBUILDER.DrawingBoard.Attribute;
import project.ERDBUILDER.DrawingBoard.Connection;
import project.ERDBUILDER.DrawingBoard.Connection2;
import project.ERDBUILDER.DrawingBoard.NamedShape;


public class SQL {

public static void main(String args[]){
       ArrayList<Connection> con = new ArrayList<>();
       
        for (int a = 0; a < con.size(); a++) {
                                    NamedShape f = con.get(a).getNamedShape1();
                                    Attribute g = con.get(a).getNamedShape2();
                                    String i = f.getName();
                                    String j = g.getName();

                                    Shape y = f.getShape();
                                    Shape y1 = g.getShape();
                                    System.out.println(i + " AND " + j + " are linked");
                                    
                                    
                                    
                                   
        }
   }    
   
}

解决方案

Create an instance of the class where you want to create the SQL statement and pass the Connection ArrayList to that class.

List<Connection> con = new ArrayList<>();
ERDBuilder x = new ERDBuilder(con);

Your ERDBuilder constructor can take a List object and use it to build a SQL statement. Or you can even do this in a method of ERDBuilder. That is your choice.

ERDBuilder x = new ERDBuilder();
List<Connection> con = new ArrayList<>();
x.buildSql(con);

If you want to do it from main then you have to declare the List as a Class level variable, the same way you have done with the ERDBuilder.

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