Why Does My JTable Show Duplicate Rows When the Underlying Data is Correct?

JTable duplicate values in row: Resolving the mystery

In response to the concern about apparently duplicate values populating a JTable, a detailed investigation has revealed that the underlying data model is indeed holding the correct data. To understand the root cause, let's delve into the provided code.

Upon calling the populate() method in the custom CollectionDataModel, the data is expected to be rendered in the table. However, the issue arises when the data is cleared before populating it. This is done through the line data.clear().

To illustrate this further, let's consider an example scenario. Suppose the data model initially contains two rows, with each row having three columns. Upon calling populate(), this data is cleared, leaving the table empty. Now, as the new collection is iterated through, only the data from the last item in the collection is reflected in the table. This occurs because the data field in the data model only retains the last row of data.

As a result, every row in the JTable displays the same data, giving the illusion of duplicate values. To resolve this, one could modify the populate() method to skip the data clearing step, thereby preserving the existing data and appending the new data to the end of the table.

Alternatively, if it's imperative to clear the data before populating, one could consider creating a new ArrayList and assigning it to the data field instead of clearing the existing data field. This way, the correct data will be maintained without causing duplicate value issues in the JTable.

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