How to change drawable source from java file?

So, I have a button to switch current language. It shows flag and country name next to it [(Flag) ENG] I want to change text and image when user clicks it, so it changes application language and displays current. I know how to change text, but have no clue how to make image change it source

Java file

public void LanguageButtonClick(View view)
{
    Button lngBtn = findViewById(R.id.languageButton);

    if(currentLanguage == Languages.English)
    {
        currentLanguage = Languages.Polish;
        lngBtn.setText("pl");
        //Set android:drawableLeft="@drawable/ic_poland"
    }
    else if (currentLanguage == Languages.Polish)
    {
        currentLanguage = Languages.English;
        lngBtn.setText("eng");
        ///Set android:drawableLeft="@drawable/ic_united_kingdom"
    }
}

xml file

<Button
    android:onClick="LanguageButtonClick"
    android:id="@+id/languageButton"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginTop="16dp"
    android:layout_marginRight="16dp"
    android:width="125dp"
    android:height="45dp"
    android:background="@drawable/language_button"
    android:drawableLeft="@drawable/ic_united_kingdom" <------------------This one
    android:text="@string/eng"
    android:textSize="18sp"
    android:textStyle="bold"
    app:backgroundTint="#FFFFFF"
    app:backgroundTintMode="multiply"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

You can use the setCompoundDrawables

Drawable drawable = getContext().getResources().getDrawable(R.drawable.ic_united_kingdom);
lngBtn.setCompoundDrawables(drawable, null, null, null);

Here's the full code

public void LanguageButtonClick(View view)
{
    Button lngBtn = findViewById(R.id.languageButton);

    if(currentLanguage == Languages.English)
    {
        currentLanguage = Languages.Polish;
        lngBtn.setText("pl");
        Drawable drawable = getContext().getResources().getDrawable(R.drawable.ic_poland);
    lngBtn.setCompoundDrawables(drawable, null, null, null);
    }
    else if (currentLanguage == Languages.Polish)
    {
        currentLanguage = Languages.English;
        lngBtn.setText("eng");
        Drawable drawable = getContext().getResources().getDrawable(R.drawable.ic_united_kingdom);
    lngBtn.setCompoundDrawables(drawable, null, null, null);
    }
}