line.split（“，”）[1]是什么意思[Java]？

Question

I came across code where i had encountered with Double.valueOf(line.split(",")[1]) I am familiar with Double.valueOf() and my problem is to understand what does [1] mean in the sentence. Searched docs didn't find anything.

while ((line = reader.readLine()) != null)
                double crtValue = Double.valueOf(line.split(",")[1]);

Answer 1

It means that your line is a String of numbers separated by commas.
eg: "12.34,45.0,67.1"

The line.split(",") returns an array of Strings.
eg: {"12.34","45.0","67.1"}

line.split(",")[1] returns the 2nd (because indexes begin at 0) item of the array.
eg: 45.0

Answer 2

It means line is a string beginning with a,b where b is in fact a number.

crtValue is the double value of b .

Answer 3

Java public String[] split(String regex)

Splits this string around matches of the given regular expression.

It

Returns: the array of strings computed by splitting this string around matches of the given regular expression

So the [1] gets the 2nd item of the array found in String[] .

Answer 4

Your code tries to get the second double value from reader.readLine() .

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1. String numbers = "1.21,2.13,3.56,4.0,5";
2. String[] array = numbers.split(","); split the input line by commma
3. String second = array[1]; get the second element from the array. Java array numeration starts from 0 index.
4. double crtValue = Double.valueOf(second); convert String to double

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Don't forget about NumberFormatException that may be thrown if the string does not contain a parsable double .