Error message local variable may not have been initialized

When I initialize an object in testClass.java (aClass aClassObject = new aClass(aIncome, aRevenue, aCost)) eclipse states that the local variables aIncome, aRevenue, aCost may not have been initialized.

I am sorry if my code is difficult to read. I am a beginner and trying to learn little bit of programming before my class starts.

import javax.swing.JOptionPane;

public class testClass {
	public static void main(String[] args) {
		
		double aIncome;
		
		String input = JOptionPane.showInputDialog("Please enter the Current assets ");
		double aRevenue = Double.parseDouble(input);
		
		String input1 = JOptionPane.showInputDialog("Please enter the Current assets ");
		double aCost = Double.parseDouble(input1);
			
		aClass aClassObject = new aClass(aIncome, aRevenue, aCost);
		System.out.println(aClassObject.toString(aClassObject));
	}

}

public class aClass {

		 private double income;
		 private double revenue;
		 private double cost; 

		public aClass(double aIncome, double aRevenue, double aCost)
		 {
			 income = aIncome;  
			 revenue = aRevenue;
			 cost = aCost;
			 income = revenue-cost;
			
		 }
		 public String toString (aClass aClassObject){
			 String answer = "the income should be" + income;
			 
			 return answer;
			 
		 }

}