Manipulando xlsx dando um erro ajuda api da apache

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package planilha;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.usermodel.Workbook;
import org.apache.poi.ss.usermodel.WorkbookFactory;



/**
 *
 * @author Usuario
 */
public class Planilha {

    /**
     * @param args the command line arguments
     */
public static void main(String[] args) throws IOException  {
FileInputStream imp =null;
FileOutputStream arquivo=null;
Workbook work=null;
        try{
            imp = new FileInputStream("C:\\Users\\Usuario\\Documents\\Meus arquivos recebidos\\teste.xlsx");
       work = WorkbookFactory.create(imp);
        
       Sheet sheet= work.getSheet("Sheet1");
       Row row= sheet.createRow(0);
       Cell cell= row.createCell(0);
       cell.setCellValue("Olá");
       Cell cell1=row.createCell(1);
       cell1.setCellValue("2");
       arquivo=new FileOutputStream("C:\\Users\\Usuario\\Documents\\Meus arquivos recebidos\\teste.xlsx");
       work.write(arquivo);
      
            
        
}
catch(Exception e){
    System.out.println("error");
}
    finally{
           
                imp.close();
                arquivo.close();
           
    }
       
   
    }
}

Exception in thread "main" java.lang.NullPointerException
	at planilha.Planilha.main(Planilha.java:53)
Java Result: 1
CONSTRUÍDO COM SUCESSO (tempo total: 6 segundos)