所以我从https://github.com/itext/itext7/releases/latest 并将它们放在与itext示例c01e01\u helloworld.java相同的文件夹中，但当我运行

javac C01E01_HelloWorld.java

我明白了

$ javac C01E01_HelloWorld.java 
C01E01_HelloWorld.java:3: error: package com.itextpdf.kernel.pdf does not exist
import com.itextpdf.kernel.pdf.PdfDocument;
                              ^
C01E01_HelloWorld.java:4: error: package com.itextpdf.kernel.pdf does not exist
import com.itextpdf.kernel.pdf.PdfWriter;
                              ^
C01E01_HelloWorld.java:5: error: package com.itextpdf.layout does not exist
import com.itextpdf.layout.Document;
                          ^
C01E01_HelloWorld.java:6: error: package com.itextpdf.layout.element does not exist
import com.itextpdf.layout.element.Paragraph;
                                  ^
C01E01_HelloWorld.java:25: error: cannot find symbol
        PdfWriter writer = new PdfWriter(dest);
        ^
  symbol:   class PdfWriter
  location: class C01E01_HelloWorld
C01E01_HelloWorld.java:25: error: cannot find symbol
        PdfWriter writer = new PdfWriter(dest);
                               ^
  symbol:   class PdfWriter
  location: class C01E01_HelloWorld
C01E01_HelloWorld.java:28: error: cannot find symbol
        PdfDocument pdf = new PdfDocument(writer);
        ^
  symbol:   class PdfDocument
  location: class C01E01_HelloWorld
C01E01_HelloWorld.java:28: error: cannot find symbol
        PdfDocument pdf = new PdfDocument(writer);
                              ^
  symbol:   class PdfDocument
  location: class C01E01_HelloWorld
C01E01_HelloWorld.java:31: error: cannot find symbol
        Document document = new Document(pdf);
        ^
  symbol:   class Document
  location: class C01E01_HelloWorld
C01E01_HelloWorld.java:31: error: cannot find symbol
        Document document = new Document(pdf);
                                ^
  symbol:   class Document
  location: class C01E01_HelloWorld
C01E01_HelloWorld.java:34: error: cannot find symbol
        document.add(new Paragraph("Hello World!"));
                         ^
  symbol:   class Paragraph
  location: class C01E01_HelloWorld
11 errors

我也试过了

javac -cp /home/user01/itext/demo/ C01E01_HelloWorld.java

i、 其中-cp指向itext jar（和c01e01\u helloworld.java）具有相同结果的位置。如何让导入行知道并使用itext jar文件？
或者这不能用一种简单的方法来完成，并且需要eclipse、maven或其他工具吗？
因此，我运行以下没有错误

javac -cp kernel-7.1.13.jar:layout-7.1.13.jar:io-7.1.13.jar C01E01_HelloWorld.java

如果我遗漏了任何jar文件，就会导致与丢失的jar相关的错误。但当我尝试

java C01E01_HelloWorld

我明白了

Error: Unable to initialize main class C01E01_HelloWorld
Caused by: java.lang.NoClassDefFoundError: com/itextpdf/layout/element/IBlockElement

我也试过了

java -cp kernel-7.1.13.jar:layout-7.1.13.jar:io-7.1.13.jar C01E01_HelloWorld

但结果略有不同

Error: Could not find or load main class C01E01_HelloWorld
Caused by: java.lang.ClassNotFoundException: C01E01_HelloWorld

所以下一步就是

$ java -cp kernel-7.1.13.jar:layout-7.1.13.jar:io-7.1.13.jar:. C01E01_HelloWorld
Exception in thread "main" java.lang.NullPointerException at C01E01_HelloWorld.main(C01E01_HelloWorld.java:21)

我的消息来源是

/*package tutorial.chapter01;*/

import com.itextpdf.kernel.pdf.PdfDocument;
import com.itextpdf.kernel.pdf.PdfWriter;
import com.itextpdf.layout.Document;
import com.itextpdf.layout.element.Paragraph;
import java.io.File;
import java.io.IOException;

/**
 * Simple Hello World example.
 */
public class C01E01_HelloWorld {

    /* public static final String DEST = "results/chapter01/hello_world.pdf";  */

    public static final String DEST = "hello_world.pdf";

    public static void main(String args[]) throws IOException {
        File file = new File(DEST);
        file.getParentFile().mkdirs();
        new C01E01_HelloWorld().createPdf(DEST);
    }

    public void createPdf(String dest) throws IOException {
        //Initialize PDF writer
        PdfWriter writer = new PdfWriter(dest);

        //Initialize PDF document
        PdfDocument pdf = new PdfDocument(writer);

        // Initialize document
        Document document = new Document(pdf);

        //Add paragraph to the document
        document.add(new Paragraph("Hello World!"));

        //Close document
        document.close();
    }
}