You must use the file class , create a file instance with the path of the file you want to check if existent . After that you must make sure that it is a file and not a directory . Afterwards you can call exist method on that file object referancing your file . Be aware that , file class in java is not representing a file . It actually represents a directory path or a file path , and the abstract path it represents does not have to exist physically on your computer . It is just a representation , that`s why , you can enter a path of a file as an argument while creating file object , and then check if that folder in that path does really exist , with the exists() method .

具有良好编码实践并涵盖所有情况的简单示例:

 private static void fetchIndexSafely(String url) throws FileAlreadyExistsException {
        File f = new File(Constants.RFC_INDEX_LOCAL_NAME);
        if (f.exists()) {
            throw new FileAlreadyExistsException(f.getAbsolutePath());
        } else {
            try {
                URL u = new URL(url);
                FileUtils.copyURLToFile(u, f);
            } catch (MalformedURLException ex) {
                Logger.getLogger(RfcFetcher.class.getName()).log(Level.SEVERE, null, ex);
            } catch (IOException ex) {
                Logger.getLogger(RfcFetcher.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
    }

参考和更多的例子在

https://zgrepcode.com/examples/java/java/nio/file/filealreadyexistsexception-implementations

使用java.io.File:

File f = new File(filePathString);
if(f.exists() && !f.isDirectory()) { 
    // do something
}

有多种方法可以实现这一点。

In case of just for existence. It could be file or a directory. new File("/path/to/file").exists(); Check for file File f = new File("/path/to/file"); if(f.exists() && f.isFile()) {} Check for Directory. File f = new File("/path/to/file"); if(f.exists() && f.isDirectory()) {} Java 7 way. Path path = Paths.get("/path/to/file"); Files.exists(path) // Existence Files.isDirectory(path) // is Directory Files.isRegularFile(path) // Regular file Files.isSymbolicLink(path) // Symbolic Link

如果使用spring框架，文件路径以classpath开头:

public static boolean fileExists(String sFileName) {
    if (sFileName.startsWith("classpath:")) {
        String path = sFileName.substring("classpath:".length());
        ClassLoader cl = ClassUtils.getDefaultClassLoader();
        URL url = cl != null ? cl.getResource(path) : ClassLoader.getSystemResource(path);
        return (url != null);
    } else {
        Path path = Paths.get(sFileName);
        return Files.exists(path);
    }
}

File f = new File(filePathString); 

这将不会创建物理文件。只会创建File类的对象。要物理创建一个文件，你必须显式地创建它:

f.createNewFile();

因此f.exists()可以用来检查这样的文件是否存在。