InputStreamReader, Buffered Reader, Java issue with reading standard input

Question

I have a standard input that contains lines of text. Each line contains 2 numbers that are separated by a comma. I need to separate the two numbers so that I can use them in another function. I don't know what would be a good way to read each line, separate the numbers and then use them to call function until there are no more lines to be read. I read the documentation regarding InputStreamReader and BufferedReader, however, since I'm relatively new to java they didn't make much sense.

public static void main(String[] args) throws IOException {
InputStreamReader reader = new InputStreamReader(System.in);
BufferedReader in = new BufferedReader(reader);

try {

    double num1 = Double.parseDouble(in.readLine());
    double num2 = Double.parseDouble(in.readLine());
    Main.function(num1,num2);
}

Andreas Dolk · Accepted Answer · 2020-06-15 21:04:33Z

2

When you call in.readLine() then you get a string, probably something like "42.1,100.2". The next step would be splitting the string and after that you can convert the split string(s) to numbers.

String line = in.readLine();                  // read one line
String[] parts = line.split(",");             // split the line around the comma(s)
double num1 = Double.parseDouble(parts[0]);   // convert the first part to double
double num2 = Double.parseDouble(parts[1]);   // convert the second part to double
Main.function(num1, num2);

Note that this only reads from one line in the file (many lines -> looping) and that this only works correctly when the input is well formatted. You probably want to lookup the trim() method on String.

answered Jun 15, 2020 at 21:04

Andreas Dolk

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2 Comments

Mathissohardlmao Over a year ago

When I do this it says index out of bounds for index[1] since length is only 1.

Andreas Dolk Over a year ago

Then your input is not "2 numbers, separated by a comma". That's why I mentioned: this snippet only works with correct input. If you just enter one number, then it fails with exactly that error.

user9565136 · Accepted Answer · 2020-06-15 21:06:29Z

0

Double is not recognize the commas instead you will have to take the input string and replace all commas with empty strings. e.g. you have this input

String input = "123,321.3" ;
input = input.replaceAll("," , "");

in result you will have this

input -> "123321.3"

Then you can parse the string to double.

Hope it will help. Regards , Erik.

answered Jun 15, 2020 at 21:06

user9565136

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