java - 1 error wont let my code compile -

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i new android programming , trying make app splits bill between people. integers wrong. know because in logcat says "caused by: java.lang.numberformatexception: invalid int: ""

here mainactivity.java 

public class mainactivity extends activity { public double x; public double y; protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.activity_main);      //button     button btn = (button) findviewbyid(r.id.button);       //edittext     edittext nop = (edittext) findviewbyid(r.id.edittext);     edittext cob = (edittext) findviewbyid(r.id.edittext2);       //getting strings     try{         x = double.valueof(nop.gettext().tostring());     } catch (numberformatexception) {         x = 0;     }      try{         y = double.valueof(cob.gettext().tostring());     } catch (numberformatexception) {         y = 0;     }      string textx = nop.gettext().tostring(); // if variable contains valid number:     if (textx != null && textx.length() > 0)         x = double.valueof();   // exception thrown method     else         x = 0;      //textview     final textview tv = (textview) findviewbyid(r.id.textview);      btn.setonclicklistener(new view.onclicklistener() {         @override         public void onclick(view v) {              double z = x / y;             tv.settext((int) z);         }     });  } }

here logcat:

08-19 07:30:28.452  16070-16070/com.elie.billsplitter e/androidruntime﹕ fatal exception: main     process: com.elie.billsplitter, pid: 16070     java.lang.runtimeexception: unable start activity componentinfo{com.elie.billsplitter/com.elie.billsplitter.mainactivity}: java.lang.numberformatexception: invalid int: ""             @ android.app.activitythread.performlaunchactivity(activitythread.java:2325)             @ android.app.activitythread.handlelaunchactivity(activitythread.java:2390)             @ android.app.activitythread.access$800(activitythread.java:151)             @ android.app.activitythread$h.handlemessage(activitythread.java:1303)             @ android.os.handler.dispatchmessage(handler.java:102)             @ android.os.looper.loop(looper.java:135)             @ android.app.activitythread.main(activitythread.java:5257)             @ java.lang.reflect.method.invoke(native method)             @ java.lang.reflect.method.invoke(method.java:372)             @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:903)             @ com.android.internal.os.zygoteinit.main(zygoteinit.java:698)      caused by: java.lang.numberformatexception: invalid int: ""             @ java.lang.integer.invalidint(integer.java:138)             @ java.lang.integer.parseint(integer.java:358)             @ java.lang.integer.parseint(integer.java:334)             @ com.elie.billsplitter.mainactivity.oncreate(mainactivity.java:25)             @ android.app.activity.performcreate(activity.java:5990)             @ android.app.instrumentation.callactivityoncreate(instrumentation.java:1106)             @ android.app.activitythread.performlaunchactivity(activitythread.java:2278)             at android.app.activitythread.handlelaunchactivity(activitythread.java:2390)             at android.app.activitythread.access$800(activitythread.java:151)             at android.app.activitythread$h.handlemessage(activitythread.java:1303)             at android.os.handler.dispatchmessage(handler.java:102)             at android.os.looper.loop(looper.java:135)             at android.app.activitythread.main(activitythread.java:5257)             at java.lang.reflect.method.invoke(native method)             at java.lang.reflect.method.invoke(method.java:372)             at com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:903)             at com.android.internal.os.zygoteinit.main(zygoteinit.java:698)

looking exception:

java.lang.runtimeexception: unable start activity componentinfo{com.elie.billsplitter/com.elie.billsplitter.mainactivity}: java.lang.numberformatexception: invalid int: ""

the error in piece of code

//getting strings x = integer.parseint(nop.gettext().tostring()); y = integer.parseint(cob.gettext().tostring());

why?
nop.gettext().tostring().equals("") or cob.gettext().tostring().equals("").

how avoid?
you must sure valid string edittext because if them empty or not contain equivaloent double string have numberformatexception.

solution?
best ways be:

  • adding validation edittext valid strings.
  • convert value if numberformatexception thrown.

try{     x = double.valueof(nop.gettext().tostring()); } catch (numberformatexception e) {     x = 0; }  try{     y = double.valueof(cop.gettext().tostring()); } catch (numberformatexception e) {     y = 1; // division / 0 throw nan }

add-on: why dont use integer.parseint()??
if create doubles cannot parse ints because lose accuracy, and, example in java (int) 1 / (int) 3 = 0 or (int) 10 / (int) 3 = 3 use double::valueof()

x = double.valueof(nop.gettext().tostring()); y = double.valueof(cob.gettext().tostring());

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