IO-字符流 练习

LineNumberReader是BufferedReader的子类, 具有相同的功能, 并且可以统计行号
    * 调用getLineNumber()方法可以获取当前行号
    * 调用setLineNumber()方法可以设置当前行号
* 
        LineNumberReader lnr = new LineNumberReader(new FileReader("aaa.txt"));
        String line;
        lnr.setLineNumber(100);                                    //设置行号    默认是从0行开始
        while((line = lnr.readLine()) != null) {
            System.out.println(lnr.getLineNumber() + ":" + line);//获取行号
        }
        
        lnr.close(); 

public class test2 {
    /*
     * 获取一个文本上每个字符出现的次数,将结果写在times.txt上
     */
    public static void main(String[] args) throws IOException {
        BufferedReader b1 = new BufferedReader(new FileReader("zzz.txt"));
        TreeMap<Character, Integer> t1 = new TreeMap<>();
        int ch ;
        while((ch = b1.read()) != -1){
            char c = (char)ch;   //向下强转
            if (!t1.containsKey(c)) {
                t1.put(c, 1);
            }else{
                t1.put(c, t1.get(c)+1);
            }  // 可以用三元运算符写
        }
        b1.close();
        BufferedWriter b2 = new BufferedWriter(new FileWriter("time.txt"));
        for (Character key : t1.keySet()) {
            switch (key) {
            case '\t':
                b2.write("\\t" + "=" + t1.get(key));
                break;
            case '\n':
                b2.write("\\n" + "=" + t1.get(key));
                break;
            case '\r':
                b2.write("\\r" + "=" + t1.get(key));
                break;
            default:
                b2.write(key + "=" + t1.get(key));
                break;
            }
            //b2.write(key + "=" + t1.get(key));  //写出键和值
            b2.newLine();
        }
        b2.close();
    }

}