从ArrayList中删除一个元素

Question

I'm trying to remove the String match "Meg" by using the ArrayList and for loop. So far I have written the code below and not sure why it's not working. I think the problem is with the below while loop

while((customerName.get(i)).equals("Meg"))
{
  customerName.remove(i);
}

Thanks in advance.

Complete code is as below:

import java.util.ArrayList;
public class CustomerLister2
{
  public static void main(String[] args)
  {
    ArrayList<String> customerName = new ArrayList<String>(); 
    customerName.add("Chris");
    customerName.add("Lois");
    customerName.add("Meg");
    customerName.add("Peter");
    customerName.add("Stewie");
    customerName.add(3, "Meg");
    customerName.add(4, "Brian");

    int currentSize = customerName.size();

    for(int i = 0; i < currentSize - 1; i++)
    {

      while((customerName.get(i)).equals("Meg"))
      {
        customerName.remove(i);
      }
    }
    for(String newStr: customerName)
    {
      System.out.println(newStr);
    }
  }
}

Answer 1

Change it to the following

for(int i = 0; i < currentSize; i++)
{
  if((customerName.get(i)).equals("Meg"))
  {
    customerName.remove(i);
    i--;  //because a new element may be at i now
    currentSize = customerName.size(); //size has changed
  }
}

Answer 2

Or if you don't have to use a for loop:

   public static void main(String[] args) {

        ArrayList<String> customerName = new ArrayList<String>();
        customerName.add("Chris");
        customerName.add("Lois");
        customerName.add("Meg");
        customerName.add("Peter");
        customerName.add("Stewie");
        customerName.add(3, "Meg");
        customerName.add(4, "Brian");

        while (customerName.remove("Meg")) {}

        for (String s : customerName) {
            System.out.println(s);
        }
    }

Answer 3

This will help you

System.out.println("Customer Name (including Meg)"+customerName);
for(int i=0; i<customerName.size(); i++)
{
  String s = customerName.get(i);
  if(s.equals("Meg"))
  {
     customerName.remove(i);
     i--;
  }
}
System.out.println("Customer Name (excluding Meg)"+customerName);

Answer 4

Use iterator customerName.iterator() (iterator() is non-static method) Iterator takes care of list's count modification. We might forget to take care of list's count modification when we use for loop.

Iterator<String> itr= customerName.iterator();
while(itr.hasNext())
{
    if(itr.next().equals("Meg")){
        itr.remove();
    }
}

Drawback also there in iterator. It doesn't work if two threads are concurrently accessing the same list object. Ex. One thread is reading and another thread is removing element from the list then it throws java.util.ConcurrentModificationException. Better to use Vector in concurrent scenario.

If you still want to use same for loop then add following line of code.

int currentSize = customerName.size();

for(int i = 0; i < currentSize; i++)
{

  while((customerName.get(i)).equals("Meg"))
  {
    customerName.remove(i);
    currentSize = customerName.size(); //add this line to avoid run-time exception.
  }
}