在实际编程中可以不用关注JVM中使用的是什么编码，而只需要关注自己输出需要采用的编码，JVM会根据你设置的编码正确操作。

1、String采用的是什么编码？

　　很多厂家根据规范实现了JVM，JVM只说明了String应该符合Unicode编码。Unicode编码只是一种编码模型，utf8,utf16,utf32都属于Unicode模型

      ，具体的信息参阅

2、为什么JAVA中Char是两个字节？

     参阅

     When Java was originally designed, it was anticipated that any Unicode character would fit in 2 bytes (16 bits), so char and Character were designed accordingly. In fact, a Unicode        character can now require up to 4 bytes. Thus, UTF-16, the internal Java encoding, requires supplementary characters use 2 code units. Characters in the Basic Multilingual Plane        (the most common ones) still use 1. A Java char is used for each code unit. This  explains it well.