Question

这是程序:(文件名是date.java）

class date {
    public static void main (String[] args) {
    int day, hour, minute;
    String firstline, half;

    firstline="the current imaginary time is:";
    day=24;
    hour=5;
    minute=36;

    String half;
    half="PM" ;


    System.out.println ("here is some program about the time kindof:");
    system.out.print (firstline) ;
    system.out.print (day) ;
    system.out.print (hour) ;
    system.out.print (":") ;
    system.out.print (minute) ;
    system.out.println (half) ;

    }
    }

这是当我尝试在终端中编译它时会发生什么：

david-allenders-macbook-pro:~ davidallender$ javac date.java
date.java:11: half is already defined in main(java.lang.String[])
    String half;
               ^
date.java:15: package system does not exist
    system.out.print (firstline) ;
              ^
date.java:16: package system does not exist
    system.out.print (day) ;
              ^
date.java:17: package system does not exist
    system.out.print (hour) ;
              ^
date.java:18: package system does not exist
    system.out.print (":") ;
              ^
date.java:19: package system does not exist
    system.out.print (minute) ;
              ^
date.java:20: package system does not exist
    system.out.println (half) ;
              ^
7 errors
david-allenders-macbook-pro:~ davidallender$

我正在网上找到一本书。现在我在关于变量的章节中。我做错了什么？

Answer 1

String half;

你已经提前一半宣布，删除这一个

system.out.print (firstline) ;

java中的类名称区分大小写。系统应该是系统

Answer 2

删除第二个'String half;'在主要。系统应该是系统。

Answer 3

变量可以在任何范围内声明一次，而System不是系统。

Answer 4

您可能希望尝试Eclipse Java IDE（集成开发环境），以便将来可以避免这些问题。它将建议修复这些简单的错误。

http://www.eclipse.org/downloads/

另外，它是免费的！

Java“XXX已在main中定义”错误

4 个答案: