swing - Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException: empty String -

i've been having problems running program compiles doesn't run properly. when run , attempt perform calculations spits out bunch errors. think has variable types. here program:

import javax.swing.*; import java.awt.*; import java.awt.event.*; public class area extends jframe implements actionlistener, itemlistener{   //row 1   jpanel row1 = new jpanel();   jlabel select = new jlabel("please select caculate area , volume of.");  //row 2   jpanel row2 = new jpanel();   jcheckbox circle = new jcheckbox("circle", false);   jcheckbox cube = new jcheckbox("cube", false);  //row 3    jpanel row3 = new jpanel();   jlabel radlab = new jlabel("radius of circle (in cm)");   jtextfield rad = new jtextfield(3);   jlabel sidelab = new jlabel("a side of cube (in cm)");   jtextfield side = new jtextfield(3);  //row4   jpanel row4 = new jpanel();    jbutton solve = new jbutton("solve!"); //row 5   jpanel row5 = new jpanel();   jlabel areacallab = new jlabel("area");   jtextfield areacal = new jtextfield(10);   jlabel volumelab = new jlabel("volume");   jtextfield volume = new jtextfield(10); public area(){   settitle("area caculator");     setsize(500,400);     setdefaultcloseoperation(jframe.exit_on_close);     setvisible(true); //disables text areas    rad.setenabled(false);   side.setenabled(false);   areacal.setenabled(false);   volume.setenabled(false); //add listeners   circle.additemlistener(this);   cube.additemlistener(this);   solve.addactionlistener(this); flowlayout 1 = new flowlayout(flowlayout.center);    setlayout(one);    row1.add(select);    add(row1);     row2.add(circle);   row2.add(cube);    add(row2);    row3.add(radlab);   row3.add(rad);   row3.add(sidelab);   row3.add(side);    add(row3);    row4.add(solve);    add(row4);    row5.add(areacallab);   row5.add(areacal);   row5.add(volumelab);   row5.add(volume);    add(row5);  } public void circlepick(){   //cube.setcurrent(false);   cube.setenabled(false);   rad.setenabled(true);  } public void cubepick(){   circle.setenabled(false);   side.setenabled(true); } @override public void itemstatechanged(itemevent event) {   object item = event.getitem();     if (item == circle){       circlepick();     }     else if (item == cube){       cubepick();     }   } @override public void actionperformed(actionevent evt){   //string radi = rad.gettext();   //string sid = side.gettext();      //circlesolve();    //cubesolve(); string radi = rad.gettext(); string sid = side.gettext();  double radius = double.parsedouble(radi); double length = double.parsedouble(sid);    double cirarea = math.pi * math.pow(radius, 2);   double cirvolume =  (4.0 / 3) * math.pi * math.pow(radius, 3);   double cubearea = math.pow(length, 2);   double cubevolume = math.pow(length, 3);   areacal.settext("" + cirarea + cubearea + "");   volume.settext("" + cirvolume + cubevolume + ""); } public static void main(string[] args) {     area = new area();   } } 

here errors printing out when attempting perform math (sorry long).

exception in thread "awt-eventqueue-0" java.lang.numberformatexception: empty string
@ sun.misc.floatingdecimal.readjavaformatstring(floatingdecimal.java:1038)
@ java.lang.double.parsedouble(double.java:548)
@ area.actionperformed(area.java:112)
...

thanks in advance help!

when calling functions:

double radius = double.parsedouble(radi); double length = double.parsedouble(sid); 

either radi or sid empty string, thats what

java.lang.numberformatexception: empty string 

tells you.
might consider adding system.out.println(raid + ", " + sid) before parsing check values empty strings , make sure, strings not empty.

double.parsedouble(string s) throws numberformatexception when given string s can not parsed double value.