Java开发网 - java程序运行时,符号 * 的用法求助

Topic: java程序运行时,符号 * 的用法求助

1.java程序运行时,符号 * 的用法求助

Posted by: java_lhl
Posted on: 2008-07-16 20:43

下面是这段小程序：

public class Args {
  public static void main(String[] args) {

double d1 = Double.parseDouble(args[0]);
double d2 = Double.parseDouble(args[2]);
double f = 0;
if(args[1].equals("+")) f= d1+d2;
else if(args[1].equals("*")) d = d1*d2;
  else{
    f = 10;
  }

System.out.println(f);
  }
}

这是运行后的结果：

E:\java>java Args 3 * 2
Exception in thread "main" java.lang.NumberFormatException: For input string: "A
rgs.class"
at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:12
24)
at java.lang.Double.parseDouble(Double.java:510)
at Args.main(Args.java:5)

但如果把*换成字符x就能算出来正确结果为： 6.0，小弟初学，不太明白
请问大家：这个*为什么会导致错误呢？

谢谢！

*2.Re:java程序运行时,符号的用法求助** [Re: java_lhl]	Copy to clipboard
Posted by: billgacsli Posted on: 2008-07-17 11:05 "*"是特殊字符，表示匹配所有，当作为参数传入时，会实际的传入当前目录下的所有文件名你可以通过下面代码打印参数就知端倪，至于为什么，不胜了了 for(int i = 0; i < args.length; i++){ System.out.println(args[i]); }

*3.Re:java程序运行时,符号的用法求助** [Re: java_lhl]	Copy to clipboard
Posted by: JiafanZhou Posted on: 2008-07-17 15:45 It cannot even pass the compiler?? d = d1*d2; ^ 1 error

*4.Re:java程序运行时,符号的用法求助** [Re: java_lhl]	Copy to clipboard
Posted by: billgacsli Posted on: 2008-07-17 22:01 那个地方应该是变量f

5.Re:java程序运行时,符号 * 的用法求助 [Re: java_lhl]

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Posted by: java_lhl
Posted on: 2008-07-17 23:45

谢谢各位！
public class Args{
  public static void main(String[] args){
    double d1 = Double.parseDouble(args[0]);
    double d2 = Double.parseDouble(args[2]);
    double d = 0;

    if(args[1].equals("+")) d = d1 + d2;
    else if (args[1].equals("x")) d = d1*d2;
    else return;

    System.out.println(d);
  }
}

在这个论坛里 d加括号容易出现别的问题，所以我换了字母，这是原来的，最后的输出语句是（ d )

*6.Re:java程序运行时,符号的用法求助** [Re: java_lhl]	Copy to clipboard
Posted by: billgacsli Posted on: 2008-07-18 12:38 哈哈刀叉都出来了

*7.Re:java程序运行时,符号的用法求助** [Re: java_lhl]	Copy to clipboard
Posted by: JiafanZhou Posted on: 2008-07-18 15:45 It is an issue here, I will forward this information to the web admin to have a look. The parenthesis does annoy me sometimes as well.

*8.Re:java程序运行时,符号的用法求助** [Re: java_lhl]	Copy to clipboard
Posted by: JiafanZhou Posted on: 2008-07-18 15:48 Tracked by the following thread link: http://www.cjsdn.net/post/view?bid=15&id=195119&sty=1#195119

*9.Re:java程序运行时,符号的用法求助** [Re: java_lhl]	Copy to clipboard
Posted by: JiafanZhou Posted on: 2008-07-23 23:46 There is a similar solution provided by 阿熊 available at the following link: http://www.cjsdn.net/post/view?bid=15&id=195119&sty=1#195119