PrintStream和PrintWriter的源码理解

PrintStream和PrintWriter的源码理解

1.PrintStream

    A PrintStream adds functionality to another output stream ,namely the ablity to print representations of various data coventiontly . Two other features are provided as well . unlike other output streams , a PrintStream never throws an IOException ; Instead , exceptional situations  merely set an internal flag that can be tested via the checkError method . Optionally , a PrintStream can be created so as to flush automatically ; this means that the flush method is automatically invoked after a byte array is written , one of the println methods is invoked , or a newline character or byte('\n') is written .

All characters printed by a PrintStream are converted into bytes by the  platform's default character encoding . the PrintWriter class should be used in the situations that require writing characters rather than bytes.

说明几点：

•                   PrintStream在另一个输出流上面添加了功能，比如方便的打印不同形式的数据
• 其他功能：能够自动flush，从不产生异常
• PrintStream只是设置了一个内部标识，当PrintStream出错时，将标识置为true ，这个能通过方法checkError检测出来
• 用平台相关编码将字符转换成字节
• 什么情况下自动flush：  1）当写”字节数组“的时候
•                                      2）当任何一个println方法被调用的时候
  
•      3）写一个换行符（newline character）
•       4)   写的string里面有换行符（byte '\n'）

废话不说，分析源码：