为什么我的方法多次打印？

Question

I have three different programs that all read in from each other. One method creates a toString method for individual objects, the second reads in a file with a list of individual objects, and the third creates an additional toString method that calls the first one and creates a toString for the second method to use. The information is printing multiple times, and I can't figure out why. iList is an array list that contains various objects. The output I am getting is correct, but it is just printing four times instead of one.

toString method in first program:

public String toString() {

  NumberFormat dollarFmt = NumberFormat.getCurrencyInstance();
  DecimalFormat percentFmt = new DecimalFormat("#.0%");

  String output = "\nDescription: " + description.trim(); 
  output += "\nCost: " + dollarFmt.format(cost); 
  output += "   Percent Depreciation: " 
     + percentFmt.format(percentDepreciated);    
  output += "\nCurrent Value: " 
     + dollarFmt.format(cost - (cost * percentDepreciated));

  if (isEligibleToScrape()) {
     output += "\n*** Eligible to scrape ***";
  }   

  if (percentDepreciatedOutOfRange()) {
     output += "\n*** Percent Depreciated appears to be out of range ***";
  }
}

toString method in third program:

public String toString() { 

  String output = ("\n" + inventoryName + "\n");

  int index = 1;
  while (index < iList.size()) {

     output += (iList.toString());  

     index++;
  }

  return output;
}

Calling toString from the third program in the second program:

Inventory myInventoryList 
     = new Inventory(inventoryName, inventoryList);

  System.out.println(myInventoryList.toString());

Answer 1

You are adding iList.toString() to the output multiple times :

  while (index < iList.size()) {

     output += (iList.toString());  

     index++;
  }

That's why it's printing multiple times.

I don't know what's the type of iList , but it looks like it's some kind of list, so you probably want to add a String representation of an element of the list to the output in each iteration of the while loop (instead of the entire list every time).

Since iList is an ArrayList, you need to change the loop to :

  int index = 0;
  while (index < iList.size()) {
     output += iList.get(index).toString();   
     index++;
  }

Or :

  for (int i=0; i<iList.size();i++)
     output += iList.get(i).toString();   

Of course it would be better to append the output to a StringBuilder instead of creating a new String in each iteration.

Answer 2

这样做： output += (iList.get(index).toString());

Answer 3

Change this

while (index < iList.size()) {
  output += (iList.toString());  
  index++;
}

to something like (assuming iList is a List )

while (index < iList.size()) {
  output += iList.get(index); // <-- toString() is implicit here  
  index++;
}

Which will get(int) the individual item to be printed (instead of printing the entire List each time) and (implicitly) invoke toString() (which you have already overridden).