paintメソッドの中身はこんな感じです。
public void paint(Graphics g){

Zu1.color = Color.green;
try {
Container root = this.getParent();
while(root.getParent() != null){
root = root.getParent();
}
FileDialog fd;
fd = new FileDialog((Frame)root,"Select Text File.",FileDialog.LOAD);
fd.setVisible(true);
String fname = fd.getDirectory() + fd.getFile();
System.out.println(fname);
File fil = new File(fname);
FileReader filFR = new FileReader(fil);
BufferedReader filBR = new BufferedReader(filFR);
StringTokenizer filST;
for(int i=0; i<132; i++){
String filS = new String(filBR.readLine());
if(i==0){//一行目は描かない
continue;
}
filS = new String(filBR.readLine());
filST = new StringTokenizer(filS);
float freq,z,ang,rz,iz;
freq = Float.parseFloat(filST.nextToken());
z = Float.parseFloat(filST.nextToken());
ang = Float.parseFloat(filST.nextToken());
rz = Float.parseFloat(filST.nextToken());
iz = Float.parseFloat(filST.nextToken());
int rzi = (int)rz;
int izi = (int)iz;
g.setColor(Zu1.color);
g.fillRect(rzi-2,-izi*10-2,4,4);
}
}catch(Exception e){}
}