Null Handling - Optional

1. Using If clause

    public static String nullToOptional(String args){
        Optional<String> op = Optional.ofNullable(args);

        if(op.isPresent()){
            System.out.println(args);
            return args;
        }else {
            System.out.println("String is NULL");
            return "empty";
        }
    }


2. Using Conditional Operator

    public static boolean nullToOptional(String args){
        Optional<String> op = Optional.ofNullable(args);

        return op.isPresent()?true:false;
    }


3. 

Method Reference in Android

1. Method Reference on Button Click event.

XML
---------------------------
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="javalibrarydemo.library.app.com.newjavatest1.MainActivity">

    <Button
        android:id="@+id/btn1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Press 'Me'"
        android:textStyle="bold"

        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>

------------------------------

Java
-------------------------------

public class MainActivity extends AppCompatActivity {

    Button btn1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

btn1 = (Button)findViewById(R.id.btn1);
      btn1.setOnClickListener(this::showMsg);

    }

    public void showMsg(View view){
        Toast.makeText(MainActivity.this, "Called", Toast.LENGTH_SHORT).show();
    }
}

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