java - Number format exception error in the code -

i having error in code state number format exception error. trying take ip address ex.172.16.10.100 & subnet mask 255.255.255.0. after taking value, trying convert them decimal binary format. getting error in line ipaddress = ipaddress + printbinaryformat(octet[i]);

could please suggest me how can sorted out problem?

import java.awt.*; import java.awt.event.*; import javax.swing.text.maskformatter; import javax.swing.*; import java.text.parseexception; import java.util.regex.pattern; import java.math.biginteger; import java.util.arrays; import java.util.stringtokenizer;  public class update extends jpanel implements actionlistener { private jbutton cmdcalculate; public jformattedtextfield txtip, txtsub;//object name txtip,txtsub private jlabel  lblcalculate, lblip, lblsub, lblnetwork, lblhost; private static string ipaddress = "",subenetaddress= "", networkaddress= "", lastaddress= "";    private jpanel pananswerarea, pannortharea, panbase, panaddressgrid, panip, pansub, panbutton;  public update()  {      super.setlayout(new borderlayout());         cmdcalculate = new jbutton("calculate");     cmdcalculate.addactionlistener(this);     lblip = new jlabel("ip address: ");     lblsub = new jlabel("subnet mask: ");     panip = new jpanel();     pansub = new jpanel();     panip.add(lblip);     pansub.add(lblsub);     maskformatter mf = null;      try {          mf = new maskformatter("***.***.***.***");      } catch (parseexception e) {         e.printstacktrace();     }      txtip = new jformattedtextfield(mf);     panip.add(txtip);     txtip.setfont(new font(font.monospaced, font.plain, 12));     txtip.setpreferredsize( new dimension( 150, 24 ));       txtsub = new jformattedtextfield(mf);     pansub.add(txtsub);     txtsub.setfont(new font(font.monospaced, font.plain, 12));     txtsub.setpreferredsize( new dimension( 150, 24 ));      lblcalculate = new jlabel("calculate network , host parts: ", jlabel.left);     lblnetwork = new jlabel("network address: ", jlabel.left);     lblhost = new jlabel("host address: ", jlabel.left);      lblnetwork.settext("network address: ");     lblhost.settext("host address: ");      pananswerarea = new jpanel(new borderlayout()); //stores network , host addresses     pannortharea = new jpanel(new borderlayout()); //north has base radio buttons, south has ip/subnet     panaddressgrid = new jpanel(new gridlayout(4,2)); //stores ip, subnet address , calculate button     panbutton = new jpanel();       pananswerarea = new jpanel(new borderlayout()); //stores network , host addresses     this.add(pananswerarea, borderlayout.south);     pananswerarea.add(lblnetwork, borderlayout.north);     pananswerarea.add(lblhost, borderlayout.south);      pannortharea = new jpanel(new borderlayout());     this.add(pannortharea, borderlayout.north);     pannortharea.add(panaddressgrid, borderlayout.south);     panaddressgrid.add(panip);     panaddressgrid.add(pansub);     panaddressgrid.add(panbutton);     panbutton.add(lblcalculate);     panbutton.add(cmdcalculate); } public void actionperformed (actionevent e) {     string strip= "";     string strsub= "";     string ipaddress = "",subenetaddress= "", networkaddress= "", lastaddress= "", inversbits= "",inversesubnetmask= "";     strip = txtip.gettext();     strsub = txtsub.gettext();      stringtokenizer st;     string[]octet=new string[4];     st = new stringtokenizer(strip,".");      for(int =0;i!=4;i++)     {         octet[i]=st.nexttoken();         ipaddress = ipaddress + printbinaryformat(octet[i]);//problem here       }   }  private static string printbinaryformat(string number) {     int decnum = integer.parseint(number),length = 0;     string binary = "", answer = "";      while( decnum > 0){          binary += integer.tostring (decnum %2);          decnum= decnum/2;      }     length =  binary.length();      (int padding = (8 - length); padding > 0; padding--)     {         answer += "0";     }      (int = length; > 0; i--)     {         answer += binary.charat(i - 1);     }      return answer; } public static void main(string[] args) {     jframe.setdefaultlookandfeeldecorated(true);// decorated border     jframe frame = new jframe("subnet calculators"); //title     frame.setdefaultcloseoperation(jframe.exit_on_close);     //frame.setsize(500, 600);      jcomponent panemain = new update();     panemain.setopaque(true);     panemain.setpreferredsize(new dimension(500, 300));// works of size of frame     frame.setcontentpane(panemain);     frame.pack();     frame.setvisible(true); } 

}

change line:

int decnum = integer.parseint(number), length = 0; 

to:

int decnum = integer.parseint(number.trim()), length = 0; 

or:

int decnum = integer.parseint(number.replaceall(" ", "")), length = 0;