用JAVA，MySQL写个折线图，出了点状况，求大神指出！：报错

这里是源码：
package demo; import java.awt.Canvas;

import java.awt.Color;

import java.awt.Graphics;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.sql.Statement;

import java.util.ArrayList;

import java.util.List;

import javax.swing.JButton;

import javax.swing.JFrame;

import javax.swing.JTextField;

import javax.swing.SwingUtilities;

public class imgshow extends  JFrame {

/**

* 

*/

private static final long serialVersionUID = 1L;

public JButton b;

mycanvas a;

public JTextField jt;

Connection kt;

String getname;

int x=0;

  int y=0;

public List<Integer> getinput;

public List<Integer> getoutput;

Statement sm;

class mycanvas extends Canvas{

/**

* 

*/

private static final long serialVersionUID = 1L;

public void paint(Graphics g){

g.drawLine(30, 0,30,500);

g.drawLine(30,500,600,500);

g.drawString("100",30,400);

g.drawString("200", 30, 300);

g.drawString("300", 30, 200);

g.drawString("400", 30, 100);

g.drawString("100", 130,500 );

g.drawString("200", 230,500 );

g.drawString("300", 330,500 );

g.drawString("400", 430,500 );

g.drawString("500", 530,500 );

g.drawString("支出/收入", 30,520 );

g.setColor(Color.red);

g.drawLine(30, 500, x,y);

//g.drawLine(x,y ,430,200);

g.drawString("balance", 400, 100);

g.setColor(Color.BLUE);

g.drawLine(30, 500, 400, 100);

}

}

imgshow(){

  this.setSize(1000,700);  

  this.setLayout(null);

      this.setTitle("波浪线展示：");

      b=new JButton("确定查询");

      b.setBounds(900, 00, 100, 30);

     a=new mycanvas();

     a.setBounds(0, 0,700, 600);

     jt=new JTextField();

     jt.setBounds(900, 30, 100, 30);

      this.add(a);

      this.add(jt);

      this.add(b);

      b.addActionListener(new act(jt));

      this.setLocationRelativeTo(null);

this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

this.setVisible(true);

}

    class act implements ActionListener{

    JTextField get;

    act(JTextField get){

    this.get=get;

    }

    public void actionPerformed(ActionEvent e) {

    String getname=get.getText(); 

    thread thread1=new thread(getname);

                 thread1.start();

       SwingUtilities.invokeLater(thread1);

    }

    }

    class thread extends Thread {

// TODO Auto-generated method stub

private String name;

    thread(String name){

  this.name=name;

   }

    public void run(){ 

  try {

List<Integer>getinput=new ArrayList<Integer>();

List<Integer>getoutput=new ArrayList<Integer>();

Class.forName("com.mysql.jdbc.Driver");

       Connection kt;

    kt = DriverManager.getConnection("jdbc:mysql://localhost:3306/bankcount","root","123");

    Statement sm=kt.createStatement();

ResultSet rs=sm.executeQuery("select input,output from informations where name='"+name+"'");

while(rs.next()){

getinput.add(rs.getInt("input"));

    getoutput.add(rs.getInt("output"));

}

repaint(getinput,getoutput);

}

catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

} catch (ClassNotFoundException e) {

// TODO Auto-generated catch block

e.printStackTrace();

} 

    }

    }  

    public void repaint(List c,List d){

    for(int j = 0;j<c.size()-1;j++){

    System.out.println(c.get(j));

    x=(int)c.get(j)+30;

    if((int)c.get(j)<=100){

    y=(int) c.get(j)+300;

    a.repaint();

    }

    if((int)c.get(j)<=200&&(int)c.get(j)>100){

        y=(int)c.get(j)+100;

        a.repaint();

        }

    if((int)c.get(j)<=300&&(int)c.get(j)>200){

        y=(int)c.get(j)-100;

        a.repaint();

        }

    if((int)c.get(j)<=400&&(int)c.get(j)>300){

            y=(int)c.get(j)-300;

        a.repaint();

            }

    }

    }

public static void main(String args[]){

new imgshow();

}

}这里是未按下按钮的效果：

 这里是按下按钮后效果：

我的本意是从数据库里取得值以后，在画出图，
但是不知道为什么只能显示数据库里的最后一条数据，但是我像画出所有的数据库里的数据，但是根本不行。
下面我给出理想的效果图：
请问大师该怎么做才能实现，我实在看不穿。