尝试仅在文件包含数字和单词的情况下读取双精度数。到目前为止,我完成的代码可以正确读取文件并打印带有数字和单词的完整列表。不确定如何排除单词并打印只读双精度数。
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
这是一个工作测试
Scanner sc = new Scanner("aaaa 1.1 bbbn3");
sc.useLocale(Locale.US);
while (sc.hasNext()) {
if (sc.hasNextDouble()) {
System.out.println(sc.nextDouble());
} else {
sc.next();
}
}
请注意,我使用了美国区域设置,以便扫描仪插入"."作为小数分隔符,在我的区域设置(默认)中它是","。另请注意,1.1 和 3(整数)均可由 nextDouble 识别