android - NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equalsIgnoreCase(java.lang.String)' on a null object reference

I am getting this error at runtime.

java.lang.RuntimeException: Unable to start activity ComponentInfo
java.lang.NullPointerException: Attempt to invoke virtual method
'boolean java.lang.String.equalsIgnoreCase(java.lang.String)' on a
null object reference

StackTrace:

01-12 03:44:54.270: E/AndroidRuntime(1437): FATAL EXCEPTION: main
01-12 03:44:54.270: E/AndroidRuntime(1437): Process: home.saket, PID: 1437
01-12 03:44:54.270: E/AndroidRuntime(1437): java.lang.RuntimeException: Unable to start activity ComponentInfo{home.saket/home.saket.addmember.Add_Update_User}: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equalsIgnoreCase(java.lang.String)' on a null object reference
01-12 03:44:54.270: E/AndroidRuntime(1437):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
01-12 03:44:54.270: E/AndroidRuntime(1437):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
01-12 03:44:54.270: E/AndroidRuntime(1437):     at android.app.ActivityThread.access$800(ActivityThread.java:144)

01-12 03:44:54.270: E/AndroidRuntime(1437):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
01-12 03:44:54.270: E/AndroidRuntime(1437):     at android.os.Handler.dispatchMessage(Handler.java:102)
01-12 03:44:54.270: E/AndroidRuntime(1437):     at android.os.Looper.loop(Looper.java:135)
01-12 03:44:54.270: E/AndroidRuntime(1437):     at android.app.ActivityThread.main(ActivityThread.java:5221)
01-12 03:44:54.270: E/AndroidRuntime(1437):     at java.lang.reflect.Method.invoke(Native Method)
01-12 03:44:54.270: E/AndroidRuntime(1437):     at java.lang.reflect.Method.invoke(Method.java:372)
01-12 03:44:54.270: E/AndroidRuntime(1437):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
01-12 03:44:54.270: E/AndroidRuntime(1437):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
01-12 03:44:54.270: E/AndroidRuntime(1437): Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equalsIgnoreCase(java.lang.String)' on a null object reference
01-12 03:44:54.270: E/AndroidRuntime(1437):     at home.saket.addmember.Add_Update_User.onCreate(Add_Update_User.java:38)

01-12 03:44:54.270: E/AndroidRuntime(1437):     at android.app.Activity.performCreate(Activity.java:5933)
01-12 03:44:54.270: E/AndroidRuntime(1437):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
01-12 03:44:54.270: E/AndroidRuntime(1437):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
01-12 03:44:54.270: E/AndroidRuntime(1437):     ... 10 more
01-12 03:44:54.272: W/ActivityManager(472):   Force finishing activity home.saket/.addmember.Add_Update_User
01-12 03:44:54.273: E/ActivityManager(472): Invalid thumbnail dimensions: 384x384

Below I am posted the codes and pointed out the error line.

Add_Update_User.java:

@Override
    protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.add_update_screen);

    // set screen
    Set_Add_Update_Screen();


    // set visibility of view as per calling activity
    String called_from = getIntent().getStringExtra("called");

    if (called_from.equalsIgnoreCase("add")) {  --->38th error line
        add_view.setVisibility(View.VISIBLE);
        update_view.setVisibility(View.GONE);
    } else {

        update_view.setVisibility(View.VISIBLE);

        add_view.setVisibility(View.GONE);
        USER_ID = Integer.parseInt(getIntent().getStringExtra("USER_ID"));

        Contact c = dbHandler.Get_Contact(USER_ID);  

        add_name.setText(c.getName());
        add_mobile.setText(c.getPhoneNumber());
        add_email.setText(c.getEmail());
        // dbHandler.close();
    }

    }

Answer

called_from must be null. Add a test against that condition like

if (called_from != null && called_from.equalsIgnoreCase("add")) {

or you could use Yoda conditions (per the Advantages in the linked Wikipedia article it can also solve some types of unsafe null behavior they can be described as placing the constant portion of the expression on the left side of the conditional statement)

if ("add".equalsIgnoreCase(called_from)) { // <-- safe if called_from is null