1. 鲜为人知的replaceAll技巧

System.out.println("foo[0]".replaceAll("\\[(\\d+)\\]", ".$1"));
//输出： foo.0

2. 构建一个重复的字符串

System.out.println(new String(new char[3]).replace("\0", "osc"));
//输出： oscoscosc

3. 按行读取字符串

BufferedReader br = new BufferedReader(new StringReader("osc1\r\nosc2\r\nosc3"));
System.out.println(br.readLine());
System.out.println(br.readLine());
//输出：
//osc1
//osc2

4. 以指定编码从文件读取

BufferedReader reader =new BufferedReader(new InputStreamReader(new FileInputStream("/home/joymufeng/file.txt"),"UTF-8"));
reader.readLine();

5. 以指定编码写入文件

Writer writer = new OutputStreamWriter(new FileOutputStream("/home/joymufeng/file.txt"), "UTF-8")
writer.write("我是字符串！");
writer.flush();
writer.close();

   也可以使用PrintWriter：

PrintWriter out = new PrintWriter("/home/joymufeng/file.txt", "UTF-8");
out.print(true);
out.print(3.14);
out.printf("%d + %d = %d".format(1, 1, 2));
out.println("我是字符串");
out.flush();
out.close();

6. 输出汉字的特定字符集编码

String code = new BigInteger(1, "你好".getBytes("utf-8")).toString(16);
System.out.println(code);

输出：

e4bda0e5a5bd