使用java

Question

我正在研究一个需要复制包含图像目录的目录的java项目。由于我是Java新手，我自己设计了下面的代码来复制目录。但我得到一个'空指针异常'错误。有人可以帮我纠正我的剧本吗？或者给我一些建议？

public CopyDir() throws IOException {
    String destFolder1 = System.getProperty("user.home")+"/desktop/pics";
    File srcFolder = new File("C:\\rkm_vidyapith\\pics");
    if (!Files.exists(Paths.get(destFolder1),null))
        new File(destFolder1).mkdirs();
    if (srcFolder.isDirectory()) {
        for (String DirList : srcFolder.list()) {
            File FileList = new File(DirList);
            for (String EachFile:FileList.list())
                Files.copy(Paths.get(EachFile),
                           Paths.get(destFolder1),
                           StandardCopyOption.REPLACE_EXISTING);
        }
    }
}

Answer 1

我认为您的代码有错误！Files.exists（Paths.get（destFolder1），null）属性null此时没有问题。 我认为有更好的方法可以做到这一点。

    import java.io.File;
    import java.io.IOException;
    import java.nio.file.Files;
    import java.nio.file.Path;

    public class FileCopy {

    /**
     * @param args
     * @throws IOException
     */
    public static void main(String[] args) throws IOException{
        File sourceDir = new File("c:/tmp/pics");
        if (sourceDir.exists()) { // if we have to copy something

            File destDir = new File(System.getProperty("user.home") + "/desktop/pics");
            destDir.mkdirs(); // ensure that we do have output directory

            // do copy with nio lib
            Path destPath = destDir.toPath();
            doCopy(sourceDir, destPath);
        } else {
            System.out.println("Source directory doesn't exists!");
        }

    }

    /**
     * Do copy.
     *
     * @param sourceDir the source dir
     * @param destPath the dest path
     * @throws IOException Signals that an I/O exception has occurred.
     */
    private static void doCopy(File sourceDir, Path destPath) throws IOException{
        for (File sourceFile : sourceDir.listFiles()) {
            if (sourceFile.isDirectory()){
                File dPath = destPath.resolve(sourceFile.getName()).toFile();
                if (!dPath.exists()){
                    dPath.mkdir();
                }
                doCopy(sourceFile, dPath.toPath());
            }
            else{
                Path sourcePath = sourceFile.toPath();
                Files.copy(sourcePath, destPath.resolve(sourcePath.getFileName()));
            }
        }
    }
}