I suggest you to create a method and make filterList.getSelectedItem().toString() into a variable. Then make use of reflection in creating a class

something like

String item = filterList.getSelectedItem().toString();

apply(createInstance(item))

public Object createInstance(String item){
  Class classDefinition = Class.forName(item);
  return classDefinition.newInstance();
}

But you have to add further validations there if the item exists or not.
But the idea is like that. Take advantage of reflection instead of using new keyword

I am working on CS50 Android track Fiftygram app. My code is working but I don’t like to see copy pasted codes.

Currently checking dropdown selected item name and using if/else if to call with representing instance of a Transformation. How can I directly call apply function with the string without using all these if and else ifs.

If I can find a way, I can fix some of the wording. For example, I can get rid of Transformation end of the strings and add it myself before calling the function.

public void applyFilter(View view) {
    if (filterList.getSelectedItem().toString() != null) {
        if (filterList.getSelectedItem().toString().equals("ToonFilterTransformation")) {
            apply(new ToonFilterTransformation());
        }
        else if (filterList.getSelectedItem().toString().equals("SepiaFilterTransformation")) {
            apply(new SepiaFilterTransformation());
        }
        else if (filterList.getSelectedItem().toString().equals("ContrastFilterTransformation")) {
            apply(new ContrastFilterTransformation());
        }
        else if (filterList.getSelectedItem().toString().equals("InvertFilterTransformation")) {
            apply(new InvertFilterTransformation());
        }
        else if (filterList.getSelectedItem().toString().equals("PixelationFilterTransformation")) {
            apply(new PixelationFilterTransformation());
        }
        else if (filterList.getSelectedItem().toString().equals("SketchFilterTransformation")) {
            apply(new SketchFilterTransformation());
        }
        else if (filterList.getSelectedItem().toString().equals("SwirlFilterTransformation")) {
            apply(new SwirlFilterTransformation());
        }
        else if (filterList.getSelectedItem().toString().equals("KuwaharaFilterTransformation")) {
            apply(new KuwaharaFilterTransformation());
        }
        else if (filterList.getSelectedItem().toString().equals("VignetteFilterTransformation")) {
            apply(new VignetteFilterTransformation());
        }
    }
}

public void apply(Transformation<Bitmap> filter) {
    if (original != null) {
        Glide
                .with(this)
                .load(original)
                .apply(RequestOptions.bitmapTransform(filter))
                .into(imageView);
    }
}