Java 数值类型之间的合法转换

                           +------+
                           | char |
                           +-+----+
                             |           +--------------------------+
                             |           |                          |
                             v           |                          v
+------+     +-------+     +-+---+     +-+----+     +-------+     +-+------+
| byte | --> | short | --> | int | --> | long | --> | float | --> | double |
+------+     +-------+     +-+-+-+     +------+     +-+-----+     +-+------+
                             | |                      ^             ^
                             | |                      |             |
                             | +----------------------+             |
                             |                                      |
                             +--------------------------------------+