title: java.lang.NumberFormatException: Invalid int: "" EXCEPTION
body: <p>If the user left the edittext empty an error occurs java.lang.NumberFormatException: Invalid int: "".
  The error comes at line</p>
  
  <pre><code> if (a=="" &amp;&amp; b=="")
  </code></pre>
  
  <p>and also at line</p>
  
  <pre><code> int result = Integer.parseInt(a) + Integer.parseInt(b);
   t1.setText(Integer.toString(result));
  </code></pre>
  
  <p><strong>Calci.java</strong></p>
  
  <pre><code>package com.example.calculator;
  
  import android.app.Activity;
  import android.app.AlertDialog;
  import android.content.Context;
  import android.content.DialogInterface;
  import android.os.Bundle;
  import android.view.View;
  import android.view.inputmethod.InputMethodManager;
  import android.widget.Button;
  import android.widget.EditText;
  import android.widget.TextView;
  
  public class Calci extends Activity {
      TextView t1;
      EditText e1, e2;
      Button add, sub, mul, div;
      Context c=this;
  
      String b, a;
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_calci);
          e1 = (EditText) findViewById(R.id.EditText01);
          e2 = (EditText) findViewById(R.id.EditText02);
          add = (Button) findViewById(R.id.add);
          sub = (Button) findViewById(R.id.sub);
          mul = (Button) findViewById(R.id.mul);
          div = (Button) findViewById(R.id.div);
          t1 = (TextView) findViewById(R.id.textView1);
          a = e1.getText().toString();
          b = e2.getText().toString();
  add.setOnClickListener(new View.OnClickListener() {
  
      @Override
      public void onClick(View arg0) {
          if (a=="" &amp;&amp; b==""){
                  AlertDialog.Builder a1 = new AlertDialog.Builder(c);
  
  
                  // Setting Dialog Title
                  a1.setTitle("Alert Dialog");
  
                  // Setting Dialog Message
                  a1.setMessage("PLEASE ENTER SOMETHING");
  
                  a1.setPositiveButton("yes",
                          new DialogInterface.OnClickListener() {
                              public void onClick(DialogInterface dialog,
                                      int button1) {
                                  // if this button is clicked, close
                                  // current activity
                                  dialog.cancel();
                              }
  
                          });
  
                  // Showing Alert Message
                  AlertDialog alertDialog = a1.create();
                  a1.show();
  
              }
  
          else{
              int result = Integer.parseInt(a) + Integer.parseInt(b);
              t1.setText(Integer.toString(result));
              InputMethodManager imm = (InputMethodManager)getSystemService(
                        Context.INPUT_METHOD_SERVICE);
                  imm.hideSoftInputFromWindow(add.getWindowToken(), 0);
          }
  
      }
  
  });
      }
  }
  </code></pre>
  
  <p><strong>LogCat:</strong></p>
  
  <pre><code>03-19 15:42:21.165: E/Trace(25381): error opening trace file: Permission denied (13)
  03-19 15:42:21.165: D/ActivityThread(25381): setTargetHeapUtilization:0.25
  03-19 15:42:21.165: D/ActivityThread(25381): setTargetHeapIdealFree:8388608
  03-19 15:42:21.165: D/ActivityThread(25381): setTargetHeapConcurrentStart:2097152
  03-19 15:42:21.385: D/libEGL(25381): loaded /system/lib/egl/libEGL_adreno200.so
  03-19 15:42:21.465: D/libEGL(25381): loaded /system/lib/egl/libGLESv1_CM_adreno200.so
  03-19 15:42:21.475: D/libEGL(25381): loaded /system/lib/egl/libGLESv2_adreno200.so
  03-19 15:42:21.475: I/Adreno200-EGL(25381): &lt;qeglDrvAPI_eglInitialize:299&gt;: EGL 1.4 QUALCOMM build:  (Merge)
  03-19 15:42:21.475: I/Adreno200-EGL(25381): Build Date: 07/09/13 Tue
  03-19 15:42:21.475: I/Adreno200-EGL(25381): Local Branch: AU_41
  03-19 15:42:21.475: I/Adreno200-EGL(25381): Remote Branch: 
  03-19 15:42:21.475: I/Adreno200-EGL(25381): Local Patches: 
  03-19 15:42:21.475: I/Adreno200-EGL(25381): Reconstruct Branch: 
  03-19 15:42:21.675: D/OpenGLRenderer(25381): Enabling debug mode 0
  03-19 15:42:24.325: D/AndroidRuntime(25381): Shutting down VM
  03-19 15:42:24.325: W/dalvikvm(25381): threadid=1: thread exiting with uncaught exception (group=0x41972378)
  03-19 15:42:24.395: E/AndroidRuntime(25381): FATAL EXCEPTION: main
  03-19 15:42:24.395: E/AndroidRuntime(25381): java.lang.NumberFormatException: Invalid int: ""
  03-19 15:42:24.395: E/AndroidRuntime(25381):    at java.lang.Integer.invalidInt(Integer.java:138)
  03-19 15:42:24.395: E/AndroidRuntime(25381):    at java.lang.Integer.parseInt(Integer.java:359)
  03-19 15:42:24.395: E/AndroidRuntime(25381):    at java.lang.Integer.parseInt(Integer.java:332)
  03-19 15:42:24.395: E/AndroidRuntime(25381):    at com.example.calculator.Calci$1.onClick(Calci.java:67)
  03-19 15:42:24.395: E/AndroidRuntime(25381):    at android.view.View.performClick(View.java:4147)
  03-19 15:42:24.395: E/AndroidRuntime(25381):    at android.view.View$PerformClick.run(View.java:17161)
  03-19 15:42:24.395: E/AndroidRuntime(25381):    at android.os.Handler.handleCallback(Handler.java:615)
  03-19 15:42:24.395: E/AndroidRuntime(25381):    at android.os.Handler.dispatchMessage(Handler.java:92)
  03-19 15:42:24.395: E/AndroidRuntime(25381):    at android.os.Looper.loop(Looper.java:213)
  03-19 15:42:24.395: E/AndroidRuntime(25381):    at android.app.ActivityThread.main(ActivityThread.java:4787)
  03-19 15:42:24.395: E/AndroidRuntime(25381):    at java.lang.reflect.Method.invokeNative(Native Method)
  03-19 15:42:24.395: E/AndroidRuntime(25381):    at java.lang.reflect.Method.invoke(Method.java:511)
  03-19 15:42:24.395: E/AndroidRuntime(25381):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789)
  03-19 15:42:24.395: E/AndroidRuntime(25381):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:556)
  03-19 15:42:24.395: E/AndroidRuntime(25381):    at dalvik.system.NativeStart.main(Native Method)
  03-19 15:42:25.685: I/Process(25381): Sending signal. PID: 25381 SIG: 9
  </code></pre>
  
  <p>Anybody have an idea how to solve these stack trace error.</p>