java中如何将输出的结果写入到文件和显示在屏幕

public class Demo {
public static Random ran = new Random();
    public static void main(String[] args) {
        try {
            solution();
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    //获取50个随机数
    public static List<Integer> test() {
        List<Integer> arr = new ArrayList<Integer>();
        for (int i = 0; i < 50; i++) {
            arr.add(i+1);
        }
        return arr;
    }
    //逻辑处理
    public static  void solution() throws Exception{
        List<Integer> res = new ArrayList<Integer>();
        List<Integer> list = test();
        for (int i = 0; i < 7; i++) {
            for(int j = 0; j< 7;j++){
                int a = ran.nextInt(list.size());
                res.add(list.get(a));
                list.remove(list.get(a));
            }
        }
        write2Txt(res.toString());//写到文本
        System.out.println("50个数字剩余的最后一个数字="+list.get(0));//输出到控制台
    }
     //字符串写出到文本
    public static void  write2Txt(String str) throws Exception{
        FileWriter fw = null;
        String path = "C:\\Users\\db2admin\\Desktop\\txt.txt";
        File f = new File(path);
        try {
            if (!f.exists()) {
                f.createNewFile();
            }
            fw = new FileWriter(f);
            BufferedWriter out = new BufferedWriter(fw);
            // FileOutputStream fos = new FileOutputStream(f); 
            // OutputStreamWriter out = new OutputStreamWriter(fos, "UTF-8"); 
            out.write(str.toString());
            out.close();
            System.out.println("===========写入文本成功========");
        } catch (IOException e) {
            e.printStackTrace();
        } 
    }
}