1.修改这个method to throw exception in two different case
- 存货不足
- quantity 范围（1...500）
2.修改 driver class to catch and handle the exceptions

import java.until.*;
import java.util.Scanner;
public class Part {

 private String ID;

 private String name;

 private int stLevel;

 private int roLevel;

 private double uPrice;

 public Part(String ID, String name, int sL, int rL, double uP){
  this.ID = ID;
  this.name = name;
  stLevel=sL;
  roLevel=rL;
  uPrice = uP;

 }

 public String getID(){return ID;}

 public int getSLevel(){return stLevel;}

 public void replenish(int qty){
  stLevel += qty;

 }

 public double supply(int qty){
  if (stLevel<qty) return -1.0;
  stLevel-=qty;
  if(stLevel<roLevel)
   System.out.println("Place order for" + ID);
  return qty*uPrice;

 }
}
class TestPart{

 public static void man(String args[]){
  Part P=new Part("s123", "Axle", 12, 80, 250.0);
  Scanner sc=new Scanner(System.in);
  boolean done=false;
  do{
   System.out.print("Enter qty:");
   int qty=sc.nextInt();
   double amt= p.supply(qty);
   if(amt<0){
    System.out.println("Insufficient Qty");
    System.out.println("Curr.stock="+p.getSLevel());
   }
   else{
    System.out.println("Cost for supplying"+p.getID()+"=" + amt);
    done = true;
   }
  }while(!done);

 }
}

原句是这样的：insufficient stock

程序代码应该没错的，题目是这样的
~recall that in our part class the supply method returns -1 when there are insufficient stock.
~this is not a good design, as there can be many dfifferent reasons why this method. for example, the quantity requested may be -ve or too large(above preset limt).
~in this case, throwing an exception is more suitable when one or more error states are detected. unlike returning a value(such as -1) it can explicitly indicate the cause of error.
!now modify the supply method to throw exception in two different cases
- insufficient stock
- incorrect quantity requested(assume valid quantity is in range 1...500
~modify the driver class to catch and handle the exceptions.

这个好像是提示还是什么，没看懂
changes needed for supply method

~when the quantity requested <= 0 or >500 throw an excption object as in: throw new Exception("Invalid amount");
~when the sock level is less than quantity requested throw as in: throw new Exception("Insufficient Stock");
~Change the method header to : public double supply(int qty) throws Exception


Changes needed in the calling method
~Place the try-catch within a loop which repeats until done is true. Place the call to supply in a try block as in:
try{
  double amt=p.supply(qty);
  System.out.println("Cost for supplying" + p.getID() + "=" + amt);
  done=true;
}

~Catch the Exception and handle it as in:
-Display the exception
-extract the exception message saving it in a string
-Depending on this message perform appropriate actions
catch(Exception e){
   System.out.println(e);
   String cause=e.getMessage();
   if(cause.indexOf("Insuff")>= 0）｛
   ..... ....
｝
else if(cause.indexOf("Invalid") >= 0)
   ...
}
}

在class TestPart里 e代表什么