我如何在Android Studio中重构此Kotlin代码

Question

import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import com.example.student.rexam.R.id.text

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
    }
    //etInput is an EditText element
    //tvOutput is a TextView element

    /**
     * listener for a button in this activity
     */


    fun filter(v: View) {

        val input = etInput.text.toString()
        val shortWords = shortWords(input)
        val builder = StringBuilder()

        for (word in shortWords) {
            builder.append("$word, ")

        }

        val output = builder.toString()

        tvOutput.setText("$output (${percentageShortWords()}%)")
    }

    val maxWordLength = 3

    fun shortWords(text: String): List<String> {

        var words = text.split(" ").toMutableList()

        val iterator = words.iterator()
        while (iterator.hasNext()) {
            if (iterator.next().length > maxWordLength) {
                iterator.remove()
            }
        }
        return words
    }

    fun percentageShortWords(): Int {


        val input = etInput.text.toString()
        var words = input.split(" ").toMutableList()
        val inputCount = words.count()
        val outputCount = shortWords(input).count()
        return ((outputCount.toDouble() / inputCount.toDouble()) * 100).toInt()
    }
}

我如何将此代码重构为改进的形式？ etInput是EditText元素，而tvOutput是TextView元素 一点点帮助将大有帮助 它的kotlin代码必须重构为替代或改进的形式。 编程新手，我真的需要