JetBrains/intellij-community · error · IllegalArgumentException

"Starting index " + startingIdx + " is greater than the tota

Error message

"Starting index " + startingIdx + " is greater than the total number of rows " + getRowsNum() + ". Starting index should be less or equal to " + getRowsNum()

What it means

DynamicNestedTable.insertRows(int, List<GridRow>) throws IllegalArgumentException when startingIdx exceeds the current row count. Insertion at the very end (startingIdx == getRowsNum()) is legal; anything beyond that would leave a gap in the row list.

Source

Thrown at grid/core-impl/src/datagrid/DynamicNestedTable.java:171

  @Override
  public void addRow(@NotNull GridRow value) {
    myRows.add(new Row(value.getRowNum(), GridRow.getValues(value)));
  }

  @Override
  public void removeRow(int rowIdx) {
    myRows.remove(rowIdx);
  }

  @Override
  public int getRowNum(int modelRowIdx) {
    return myRows.get(modelRowIdx).rowNum;
  }

  @Override
  public void insertRows(int startingIdx, List<GridRow> rows) {
    if (startingIdx > getRowsNum()) {
      throw new IllegalArgumentException(
        "Starting index " +
        startingIdx +
        " is greater than the total number of rows " +
        getRowsNum() +
        ". Starting index should be less or equal to " +
        getRowsNum()
      );
    }

    // Correctly replace existing rows with new rows from the list
    int endIndex = min(startingIdx + rows.size(), getRowsNum());
    for (int i = startingIdx; i < endIndex; ++i) {
      setRow(i, rows.get(i - startingIdx)); // Use (i - startingIdx) to correctly index into 'rows'
    }

    // Add any remaining new rows beyond the existing table size
    if (rows.size() > getRowsNum() - startingIdx) {
      for (int i = endIndex; i < startingIdx + rows.size(); ++i) {

View on GitHub (pinned to be881553f2)

Solutions

Clamp: use Math.min(startingIdx, table.getRowsNum()) when appending at the end is the intended semantics.
Recompute startingIdx from the live row count immediately before each insertRows call.
Insert blocks in descending original-index order so earlier inserts do not shift later positions.

Example fix

// before
table.insertRows(startingIdx, rows);

// after
int safeIdx = Math.min(startingIdx, table.getRowsNum());
table.insertRows(safeIdx, rows);

Defensive patterns

Strategy: validation

Validate before calling

int safeIdx = Math.min(startingIdx, table.getRowsNum());
table.insertRows(safeIdx, rows);

Prevention

Clamp insertion indexes to the live row count.
When inserting multiple blocks, recompute each block's index after the previous insert.

When it happens

Trigger: Calling insertRows after rows were concurrently removed so that a previously valid startingIdx now exceeds the count; computing the insert position as rowsNum() + offset; passing an already-shifted index after an earlier insert in the same batch.

Common situations: Paste/drag-drop of multiple row blocks where each block's index is precomputed; a table refresh shrinking the row list between index calculation and the insert call.

Related errors

AI-assisted analysis of JetBrains/intellij-community@be881553f2 (2026-08-14). Data as JSON: /api/errors/675a69a187308cac. Report an issue: GitHub.