Java:une phrase surligné

import java.io.*; 
public class Invest  
{ 
  public static void main(String[]args) 
  { 
  Float principalAmount=new Float(0);//converting number to object 
  Float interestRate=new Float(0); 
  int numYears=0; 
  try 
  { 
   DataInputStream in=new DataInputStream(System.in); 
   System.out.print("Enter principal Amount:"); 
   System.out.flush(); 
   String principalString=in.readLine(); 
   principalAmount=Float.valueOf(principalString);//string object to number object 
   System.out.print("Enter interest Rate:"); 
   System.out.flush(); 
   String interestString=in.readLine(); 
   interestRate=Float.valueOf(interestString); 
   System.out.print("Enter Number of years:"); 
   System.out.flush(); 
   String yearsString=in.readLine(); 
   numYears=Integer.parseInt(yearsString);//numeric strings to numbers 
  } 
  catch(IOException e) 
  { 
   System.out.println("I/O error"); 
   System.exit(1); 
  } 
  float value=loan(principalAmount.floatValue(),interestRate.floatValue(),numYears); 
  printline(); 
  System.out.println("Final Value="+value); 
  printline(); 
  } 
  //Method to compute value 
  static float loan(float p, float r, int n) 
  { 
   int year=1; 
   float sum=p; 
   while(year<=n) 
   { 
    sum=sum+(1+r); 
    year=year+1; 
   } 
   return sum; 
  } 
  //method to draw a line 
  static void printline() 
  { 
   for(int i=1;i<=30;i++) 
   { 
    System.out.print("="); 
   } 
   System.out.println(""); 
  } 
   
}