System类--标准输入输出流

System类中的两个成员变量：

    public static final InputStream in     // The "standard" input stream.
    public static final PrintStream out   //The "standard" output stream. 
    InputStream is = System.in;
    PrintStream ps = System.out;

标准输出流的高效输出：

        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));

        bw.write("1111");
        bw.newLine();

        bw.write("2222");
        bw.newLine();

        bw.write("3333");
        bw.newLine();

        bw.flush();
        bw.close();

标准输入流的高效输出：一行一行的输入数据

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

        System.out.println("请任意输入：");
        String line = br.readLine();
        System.out.println("你输入是：" + line);

请任意输入：
12
你输入是：12