从混合文件中读取双数字 [英] Reading double numbers from mixed file

问题描述

试图读取只有文件包含数字和单词的双数字。到目前为止，我所做的代码正确地从文件中读取，并用数字和文字打印完整列表。

  public void doubleFromFile（）
 {
扫描仪扫描=新扫描仪（System.in）; 
 
扫描仪fileScan; 
布尔值validName = false; 
 double num = 0.0; 
 
 do 
 {
 
 System.out.print（Enter file name：）; 
 String str = scan.nextLine（）; 
 
 try 
 {
 
 fileScan = new Scanner（new File（str））; 
 validName = true; 
 
而（fileScan.hasNextLine（））
 {
 
尝试
 {
 
海峡= fileScan.nextLine（） ; 
 num = Double.parseDouble（str）; 
 
 System.out.println（str）; 
 
 catch（NumberFormatException nfe）
 {
 System.out.println（不是双数）; 
} 
 
 
} // end while 
 
} //结束尝试
 
 
 
 catch（FileNotFoundException fnfe）
 {
 System.out.println（Invalid File name：enter again）; $！
 
 $ b} while（！validName）; 
 
} //结束doubleFromFile方法
  

解决方案

这是一个工作测试

  Scanner sc = new Scanner（aaaa 1.1 bbb\\\
3）; 
 sc.useLocale（Locale.US）; 
 while（sc.hasNext（））{
 if（sc.hasNextDouble（））{
 System.out.println（sc.nextDouble（））; 
} else {
 sc.next（）; 
 
 
 
 
 
 
 
请注意，我使用了美国语言环境， 。作为小数点分隔符，在我的语言环境中（默认）是，。还要注意，1.1和3（整数）都被nextDouble  
识别
Trying to read double numbers only where the file contains numbers and words. Code i have done so far reads from file properly and prints full list with numbers and words. Not sure how to exclude words and print read only double numbers.
 public void doubleFromFile()
 {
              Scanner scan = new Scanner(System.in);

     Scanner fileScan;
     boolean validName = false;
    double num = 0.0;

     do
     {

         System.out.print("Enter file name: ");
         String str = scan.nextLine();

        try 
        {

            fileScan = new Scanner(new File(str));
            validName = true;

        while(fileScan.hasNextLine())
        {

            try
            {

            str = fileScan.nextLine();
            num = Double.parseDouble(str);

      System.out.println(str);
            }
             catch (NumberFormatException nfe) 
             {
                System.out.println("is not a Double number");
             }   


        }//end while

        }// end try



         catch (FileNotFoundException fnfe)
           {
              System.out.println("Invalid File name: enter again");
           }

     }while(!validName);

  }//end doubleFromFile method

解决方案
Here is a working test
    Scanner sc = new Scanner("aaaa 1.1 bbb\n3");
    sc.useLocale(Locale.US);
    while (sc.hasNext()) {
        if (sc.hasNextDouble()) {
            System.out.println(sc.nextDouble());
        } else {
            sc.next();
        }
    }
Note that I used US locale so that Scanner interpets "." as decimal separator, in my locale (default) it is ",". Also note that both 1.1 and 3 (integer) are recognized by nextDouble


                        
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