如何获得用户输入中给出的位数

Question

if user is asked to enter the coefficients of variables for an equation and the number of variables is unknown for example

enter coefficients of equation 1 : 3 4 9 6
enter coefficients of equation 2 : 3 7 8 1 2

so how to know number of coefficients entered so we can use them in loop to create matrix and how to extract each digit into double in order to create a matrix like this form

3.0 4.0 9.0 6.0
3.0 7.0 8.0 1.0 2.0

ie if I want to create matrix with these coefficients how i can know the number of variables ie times of iterations.

for(int i=0; i<? ; i++)
{
  for(int j=0; j<? ; j++)
  //create the matrix

}

Answer 1

Use String.split and iterate over its elements:

Example:

public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
    System.out.println("enter coefficients of equation 1 :");
    String l1 = scan.nextLine();
    String[] elementL1 = l1.split(" ");
    System.out.println(elementL1.length);
    for (int i = 0; i < elementL1.length; i++) {
        System.out.println("Element "+ elementL1[i]);

    }
}

and do the same for the equation 2

Answer 2

Split input coefficients by space char, then create matrix

something like that

String[] numbers1 = line1.split("\s")
String[] numbers2 = line2.split("\s")

double [][] arr = new double[numbers1.length][numbers2.length]

then fill with values:

for (int i; i < numbers1.length; i++) {
    for (int j; j < numbers2.length; j++) {
        // do something
    }
}

Answer 3

how to know number of coefficients entered? you can put the "3 4 9 6" into an array ,them split it by blank" ".you will get int[] coefficients.Then the number you want is coefficients.length