Androidでおみくじアプリ

MainActivity.java

import android.graphics.Color;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import java.util.Arrays;
import java.util.Random;

public class MainActivity extends AppCompatActivity {

    private final String[] fortunes = {"大吉", "吉", "中吉", "小吉", "凶"};

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

        final Button button = findViewById(R.id.drawOmikujiButton);
        button.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                // Code here executes on main thread after user presses button
                Log.v("MainActivity", "Button Clicked");
                TextView tv = findViewById(R.id.fortuneTextView);
                int n = fortuneIndexAtRandom();
                String colorString = fortuneTextColor(n);
                tv.setText(fortunes[n]);
                tv.setTextColor(Color.parseColor(colorString));
            }
        });
    }

    private int fortuneIndexAtRandom() {
        // 配列fortunesのインデックスをランダムで返す関数
        Random rnd = new Random();
        return rnd.nextInt(fortunes.length);
    }

    private boolean isDaikichi(int fortune_index) {
        // 返された運勢が大吉か判定する関数
        int daikichi_index = Arrays.asList(fortunes).indexOf("大吉");
        return fortune_index == daikichi_index;
    }

    private String fortuneTextColor(int fortune_index){
        // 運勢の文字の色を表す文字列を返す関数
        if (isDaikichi(fortune_index)) {
            return "#ff0000";
        } else {
            return "#808080";
        }
    }
}