[英]Checking if a file exists in java
因此,以下程序应将输入和输出文件作为命令行参数。
class FileCopy
{
public static void main(String[] args) throws IOException
{
String infile = null;
String outfile = null;
BufferedReader stdin = new BufferedReader(new InputStreamReader(System.in));
if (args.length >= 2) //both files given via command line
{
infile = args[0];
if (fileExists(infile) == false)
{
infile = getInputFile();
}
outfile = args[1];
}
else if (args.length == 1) //input file given via command line
{
infile = args[0];
outfile = getOutputFile(infile);
}
else //no files given on command line
{
infile = getInputFile();
outfile = getOutputFile(infile);
}
//create file objects to use
File in = new File(infile);
File out = new File(outfile);
/*
*rest of code
*/
}
//get the input file from the user if given file does not exist
public static String getInputFile() //throws IOException
{
BufferedReader stdin = new BufferedReader(new InputStreamReader(System.in));
String fileName = null;
boolean haveFile = false;
while(haveFile == false)
{
System.out.println("Enter a valid filename for input:");
System.out.print(">> ");
try
{
fileName = stdin.readLine();
}
catch (IOException e)
{
System.out.println("Caught exception: " + e);
}
haveFile = fileExists(fileName);
}
return fileName;
}
//get the output file and test things
public static String getOutputFile(String infile)
{
BufferedReader stdin = new BufferedReader(new InputStreamReader(System.in));
File input = new File(infile);
String filename = null;
boolean more = true;
while(more)
{
System.out.println("Enter a valid filename for output:");
System.out.print(">> ");
try
{
filename = stdin.readLine();
}
catch (IOException e)
{
System.out.println("Caught exception: " + e);
}
File output = new File(filename);
if (output.exists())
{
more = false;
}
if (filename == infile)
{
int selection;
String inputString = null;
System.out.println("The output file given matches the input file. Please choose an option:");
System.out.println("1) Enter new filename");
System.out.println("2) Overwrite existing file");
System.out.println("3) Backup existing file");
System.out.print(">> ");
try
{
inputString = stdin.readLine();
}
catch (IOException e)
{
System.out.println("Caught exception: " + e);
}
selection = Integer.valueOf(inputString);
switch (selection)
{
case 1: //new filename
case 2: //overwrite
case 3: //backup
default: System.exit(0);
}
}
}
return null;
}
//check the given file to see if it exists in the current working directory
public static boolean fileExists(String n)
{
return (new File(n)).exists();
}
}
我相信您错过了一个细节:
当程序只有一个参数( args.length == 1
)时,即仅定义输入文件时, fileExists()
不调用fileExists()
; infile
设置为args[0]
,完全没有验证。 你应该添加一个特定的检查,你已经做了两个参数的情况下。
我也遇到了类似的问题。 我在eclipse下工作,必须在当前目录中指定“ src / file.txt”,在src目录中有一个名为“ file”的文件。
注意:它没有命名为“ file.txt”(这导致字符串被解释为“ file.txt.txt”!)。
假设您在“ src”目录中有一个名为“ file”的文件,请尝试在此处对此程序进行测试:
import java.io.File;
public class FileChecker {
public static boolean Exists( String file )
{
System.out.println("File being checked: " + file);
return( (file.length()) > 0 && (new File(file).exists()) );
}
public static void main( String[] args )
{
File dir = new File("src");
System.out.println("List of files in source directory: ");
if( dir.isDirectory()){
File[] filenames = dir.listFiles();
for( Object file : filenames ) {
System.out.println(file.toString());
}
}
else
System.out.println("Directory does not exist.");
if(FileChecker.Exists("src/file.txt"))
System.out.println("File exists");
else
System.out.println("File does not exist");
}
}
它将在源目录中打印出当前文件,以便您可以查看该文件是否确实存在,然后可以测试该文件是否确实存在。 对我有效。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.