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.

Setting i and j to 0 inside their respective for loops seems like a possible logic error to me. — Anthony Grist
– Anthony Grist, Commented Mar 11, 2013 at 15:39
There's no such thing as an ArrayList<Object<String>>, because class Object does not have type parameters (Object<String> is invalid). — Jesper
– Jesper, Commented Mar 11, 2013 at 15:40

Community · Accepted Answer · 2017-05-23 11:57:25Z

4

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++;
}

edited May 23, 2017 at 11:57

CommunityBot

11 silver badge

answered Mar 11, 2013 at 15:38

alno

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Comments

Fortega · Accepted Answer · 2013-03-11 15:43:23Z

3

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++;
  }
}

answered Mar 11, 2013 at 15:43

Fortega

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2 Comments

alno Over a year ago

I think what such increment isn't something desired, as each of counters becomes zero again on next iteration. So there is also need to move i=0 and j=0 one level up

Hoggie1790 Over a year ago

It works! Thanks for all the help guys. Silly mistakes can be such a hassle. Thanks again.

Iswanto San · Accepted Answer · 2013-03-11 15:47:05Z

2

Change this:

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

to:

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

edited Mar 11, 2013 at 15:47

answered Mar 11, 2013 at 15:40

Iswanto San

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