Exemplifies the lack of safety when using Java

NullableImmutable.java

class ExampleActivity extends AppCompatActivity {

    private String foo = "Bar";

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

        foo = getSomething();

        doSomething(foo); //perfectly valid Java code
    }
}


// Change to this for safety:

class ExampleActivity extends AppCompatActivity {

    private String foo = "Bar";

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

        foo = getSomething();
        
        if (foo != null){
            doSomething(foo); //Now we know it's not null, right? Do we?
        }
    }
}