Iterating through ArrayList <Object<String>>

Question

I'm having some trouble iterating through ArrayList. I have a class named Row which extends ArrayList<String>. I have another class named Table which extends ArrayList<Row>.

I am trying to iterate through the Table class to convert the ArrayList of Rows to a two-dimensional array of Strings.

Here is my code for the Table class:

public class Table extends ArrayList<Row>
{
public Row[] appArray; //Array of single applicant details
public String tableArray[][]; //Array of every applicant
private ArrayList<Row> ar;
private Row r;

public Table()
{
}

public void addApplicant(Row app)
{
    add(app);
    displayable();
}

public void convertToArray()
{
    int x = size();
    appArray=toArray(new Row[x]);
}

public void displayable()
{
int i,j;
for (Row r: ar)
   i=0;
    for(String s: r){
        j=0;
        tableArray[i][j]=s;
        j++;
    }

}}

and here is the Row class:

public class Row extends ArrayList<String>
{
public Row(String appNumber, String name, String date, String fileLoc, String country, Table table)
{
    addDetails(appNumber,name,date,fileLoc,country);
    table.addApplicant(this);
}

public void addDetails(String appNumber, String name, String date, String fileLoc, String country)
{
    add(appNumber);
    add(name);
    add(date);
    add(fileLoc);
    add(country);
}}

The method i am having trouble with is displayable() in the Table class. It tells me i may not have been initialized However if I initialize it in the second for each loop it will only iterate through the first element in my Table ArrayList?

Thanks in advance for any pointers.

Answer 1

You just missed block in for (Row r: ar) loop.

Also, as Fortega noted, you never increment i in your code, and I suppose that you zero your counters in wrong place.

So, instead of:

for (Row r: ar)
   i=0;
   for(String s: r){
     j=0;
     tableArray[i][j]=s;
     j++;
   }

You should write something like:

i=0;
for (Row r: ar) {
  j=0;
  for(String s: r){
    tableArray[i][j]=s;
    j++;
  }
  i++;
}

Or better to narrow down visibility area of counters and join declarations with initializations:

// Remove previous declarations

int i=0;
for (Row r: ar) {
  int j=0;
  for(String s: r){
    tableArray[i][j]=s;
    j++;
  }
  i++;
}

Answer 2

The displayable method has two errors:

• the first for-loop does not have {}
• i is not incremented (i++; missing)

code:

public void displayable()
{
  int i,j;
  for (Row r: ar){
    i=0;
    for(String s: r){
        j=0;
        tableArray[i][j]=s;
        j++;
    }
    i++;
  }
}