如何让JavaPoet生成类文字？

implementation 'com.squareup:javapoet:1.13.0'

String packageName = "com.example";
String className = "MyClass";
JavaFile javaFile = JavaFile.builder(packageName, ClassName.get(packageName, className))
        .build();

TypeSpec.Builder classBuilder = TypeSpec.classBuilder(className)
        .addModifiers(Modifier.PUBLIC);

// 添加字段
FieldSpec fieldSpec = FieldSpec.builder(String.class, "message")
        .addModifiers(Modifier.PRIVATE)
        .build();
classBuilder.addField(fieldSpec);

// 添加构造方法
MethodSpec constructorSpec = MethodSpec.constructorBuilder()
        .addModifiers(Modifier.PUBLIC)
        .addParameter(String.class, "message")
        .addStatement("this.message = message")
        .build();
classBuilder.addMethod(constructorSpec);

// 添加方法
MethodSpec methodSpec = MethodSpec.methodBuilder("printMessage")
        .addModifiers(Modifier.PUBLIC)
        .returns(void.class)
        .addStatement("System.out.println(message)")
        .build();
classBuilder.addMethod(methodSpec);

javaFile = javaFile.toBuilder()
        .addType(classBuilder.build())
        .build();

try {
    javaFile.writeTo(new File("src/main/java"));
} catch (IOException e) {
    e.printStackTrace();
}