Question

这是我的代码：

public static double columnSum(String filename, int column) {
    double sum = 0;

    try {
        Scanner scan = new Scanner(new File(filename));
        while (scan.hasNextLine()) {
            String s = scan.nextLine();
            sum = sum + Double.parseDouble(s.split(",")[1]);
        }
    } catch (FileNotFoundException e) {
        System.out.println("Inout file " + filename + " does not exist");
    }
    return sum;
}

为了避免出现NumberFormatException错误，我想尝试跳过文本文件的第一行，但是我不知道该怎么做。 >

这是要读取的文件的示例

Date,Temperature High,Temperature Low,Rain 
Junk line useless, data, at, every, column, in, this, line
Sat 3/7/2015,62,26,0 
Sun 3/8/2015,51,46,0.23 
Sat 3/14/2015,68,56,0 
useless, data, at, every, column, in, this, line. 
Sun 3/15/2015,69,54,0 
Mon 3/30/2015,78,60,0 
Tue 3/31/2015,84,65,0 
Wed 4/1/2015,81,66,0.04 
Thu 4/2/2015,85,69,0 
Fri 4/3/2015,74,60,0 
More junk 
Sat 4/18/2015,82,58,0.21 
Sat 4/25/2015,87,54,0 
Sun 4/26/2015,85,58,0.12 
Even more useless data. 
Sat 7/4/2015,94,77,0 
Sun 7/5/2015,84,79,0 
Mon 7/6/2015,93,78,0

Answer 1

可以做到

Scanner scan = new Scanner(new File(filename));
// skip first line
if(scan.hasNextLine()){
    scan.nextLine();
}
// then read the rest
while(scan.hasNextLine()){
    String s = scan.nextLine();
    sum = sum + Double.parseDouble(s.split(",")[1]);
}

也请不要忘记关闭Scanner。然后您的代码应该像这样

public static double columnSum(String filename, int column) {
    double sum = 0;

    try(Scanner scan = new Scanner(new File(filename))) {
        if(scan.hasNextLine()){
            scan.nextLine();
        }
        while (scan.hasNextLine()) {
            String s = scan.nextLine();
            sum = sum + Double.parseDouble(s.split(",")[1]);
        }
    } catch (FileNotFoundException e) {
        System.out.println("Inout file " + filename + " does not exist");
    }
    return sum;
}

Answer 2

in the comments中所述的另一种解决方案是将演员表放在try catch块中。由于NumberFormatException也可以在文件中的任何地方发生。

public static double columnSum(String filename, int column) {
    double sum = 0;
    Scanner scan = null;
    try {
        scan = new Scanner(new File(filename));
        while (scan.hasNextLine()) {
            String s = scan.nextLine();
            try {
                sum = sum + Double.parseDouble(s.split(",")[1]);
            } catch (NumberFormatException n) {
                // Do something else to handle it, or do nothing.
            }
        }
    } catch (FileNotFoundException e) {
        System.out.println("Inout file " + filename + " does not exist");
    } finally {
        scan.close(); // Close it regardless of the result
    }
}

我可以对我的代码执行什么操作以跳过输入文本文件的第一行？

2 个答案: