I am getting error codes where it is saying num1 den1 num2 and den2 have not been initialized. I need help initializing these variables. Using Java

Declare double variables num1, den1, num2, and den2, and read each variable from input in that order. Find the difference of the fractions num 1/ den 1 and num 2/ den 2 and assign the result to fractionDifference. The calculation is: difference =den1num1den2num2 Ex: If the input is 2.01.04.04.5, the output is: 1.11 Note: Assume that den1 and den2 will not be 0