Bug 60417

Invoking 

org.apache.poi.ss.usermodel.Sheet.autoSizeColumn(int column)

in an interrupted thread (interrupted flag = "true") swallows the interrupted exception and resets the interrupted flag to "false". 
Therefore further checks whether the thread was interrupted or not will fail. This might cause some trouble.

This bug can be observed using both "HSSF" and "XSSF" workbooks (tested with the current beta-version (3.16-beta1-20161120)).

Code example to reproduce the bug:


import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.usermodel.Workbook;

public class MainClass {

	public static void main(String[] args) {

		Thread workerThread = new WorkerThread();
		workerThread.start();

		System.out.println("Main thread will go to sleep for 2 seconds...");
		try {
			Thread.sleep(2000);
		} catch (InterruptedException e) {
			Thread.currentThread().interrupt();
			System.out.println("Main thread interrupted while sleeping...");
		}
		System.out.println("Main thread woke up...");
		workerThread.interrupt();
		System.out.println("Interrupting worker thread...");
	}

	public static class WorkerThread extends Thread {

		private final Workbook workbook;

		public WorkerThread() {
			// this.workbook = new XSSFWorkbook();
			this.workbook = new HSSFWorkbook();
		}

		@Override
		public void run() {
			Sheet sheet = this.workbook.createSheet();

			for (int i = 0; i < 10; ++i) {
				sheet.createRow(i).createCell(0).setCellValue("Row " + i);
				System.out.println("\tWorkerThread - Before autosize: interrupted = " + this.isInterrupted());
				sheet.autoSizeColumn(0);
				System.out.println("\tWorkerThread - After autosize: interrupted = " + this.isInterrupted());
				++i;
				try {
					Thread.sleep(1000);
				} catch (InterruptedException e) {
					this.interrupt();
					System.out.println("\tWorkerThread - Interrupted while sleeping...");
				}
			}
		}
	}
}


Output:

Main thread will go to sleep for 2 seconds...
	WorkerThread - Before autosize: interrupted = false
	WorkerThread - After autosize: interrupted = false
	WorkerThread - Before autosize: interrupted = false
	WorkerThread - After autosize: interrupted = false
Main thread woke up...
Interrupting worker thread...
	WorkerThread - Interrupted while sleeping...
	WorkerThread - Before autosize: interrupted = true
	WorkerThread - After autosize: interrupted = false
	WorkerThread - Before autosize: interrupted = false
	WorkerThread - After autosize: interrupted = false
	WorkerThread - Before autosize: interrupted = false
	WorkerThread - After autosize: interrupted = false

As one can clearly see, the interrupted flag is reset when autoSizeColumn(int i) is invoked.

The problem seems to occur somewhere deep in java.awt.font.TextLayout. Thus it's probably out of your scope to fix "the real bug".
However, I think it's still worth to have a look at it (and to be aware of this bug).