搜索字符串并使用PDFBox为PDF文件打印下5行

Question

我不明白语句中的错误（（p = scan.next（））！= null）。通过使用扫描仪对象我想在搜索字符串之后打印行if（p.startsWith（“START”））。 scanner对象在main中抛出java.util.NoSuchElementException。

import java.io.File;
import java.io.IOException;
import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.encryption.InvalidPasswordException;
import org.apache.pdfbox.text.PDFTextStripper;
import org.apache.poi.poifs.filesystem.POIFSFileSystem;
public class ReadWriteTest {
static int i;
    /**
     * @param args
     * @throws IOException 
     * @throws InvalidPasswordException 
     */
    public static void main(String[] args) throws InvalidPasswordException, IOException {
        POIFSFileSystem fs = null;
        PDDocument pdDoc = null;
        String target_dir = "E:\\TEST_pdfs";
        File dir = new File(target_dir);
        File[] files = dir.listFiles();
        {
        for ( int s=0;s<files.length;s++){
        if(files[s].isFile()){
        pdDoc = PDDocument.load(files[s]);
        //fs = new POIFSFileSystem(new FileInputStream(files[s]));
        PDFTextStripper Stripper =  new PDFTextStripper();
        String st = Stripper.getText(pdDoc);
        String linesp = System.lineSeparator();
        String[] paragraphs = st.split(linesp);
        for(String p: paragraphs){
            Scanner scan = new Scanner(p);
            while((p=scan.next())!=null) {
                if(p.startsWith("START"))
                    do{
                        i++;
                        String nextline = scan.next();
                        System.out.println(nextline); 
                                        }while(i<5);
            }
            }
        }

        }}}}

Error :
Exception in thread "main" java.util.NoSuchElementException
    at java.util.Scanner.throwFor(Scanner.java:862)
    at java.util.Scanner.next(Scanner.java:1371)
    at ReadWriteTest.main(ReadWriteTest.java:35)