Java錯誤

Question

這裏「XXX在主已經定義」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) ; 

    } 
    } 

這裏是發生了什麼當我嘗試編譯它在終端：

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$ 

即時通訊從我在網上找到的一本書學習。現在我在關於變量的章節中。我做錯了什麼？

Answer 1

String half; 

你已經宣佈半前

，刪除此一個

system.out.print (firstline) ; 

類名在Java是區分大小寫的。系統應該是系統

Answer 2

刪除第二個'String half;'主要。系統應該是系統。

Answer 3

變量可以在任何範圍內聲明一次，它不是系統的System。

Answer 4

您可能想嘗試Eclipse Java IDE（集成開發環境），以便將來避免這些問題。它會建議修復這些簡單的錯誤。

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

而且，它是免費的！