Regular local variables in source code are defined within a block , which may be the entire method body or some nested block 源代码中一般的本地变量都定义在一个块中,这个块可能是一个完整的方法体或者是一个嵌套块。
A local variable , already declared in an enclosing block and therefore visible in a nested block , cannot be redeclared in the nested block 一个语句块里的变量,可以被其他语句块再次声明,但是不可以在嵌套语句块声明,但是在嵌套块里他是可视的。