java - 我想删除一个文件并将新文件重命名为旧文件

Question

如果之前有人问过这个问题，请原谅我，但我正在尝试将旧文件中的一些行写入临时文件，然后在删除旧文件之前将临时文件重命名为旧文件。下面是我尝试过的一些代码，使用通常的 File .delete() 和 .renameTo()，加上创建一个新的 public static void Delete 函数，但它总是最终创建临时文件而不删除或重命名。

        String lectid = jLabel1.getText().trim();
        String passw = Lpass.getText().trim();
        String name = LName.getText().trim();
        String email = Lemail.getText().trim();
        //trim will make sure spaces are ignored
        //File temp = new File("lectemp.txt");
        try {
            Scanner sc = new Scanner(new File("lecturer.txt")).useDelimiter(",");
            //FileWriter writer = new FileWriter("lectemp.dat", true);
            FileWriter writer = new FileWriter("lectemp.txt", true);
            BufferedWriter print = new BufferedWriter(writer);
            sc.nextLine();
            while (sc.hasNextLine()) {
                String swap = sc.nextLine(); //putting it before the while statement causes it to crash
                if(swap.contains(lectid + ",")){
                    print.newLine();
                    print.write(lectid + "," +name+ "," +passw+ "," +email);

                }else{
                    print.newLine();
                    print.write(swap);
                }               
            }
            sc.close();
            print.close();
            writer.close();
            File old = new File("lecturer.txt");
            if(old.delete()){
                System.out.println("deleted");
            }else{
                System.out.println("not deleted");
            }

File old = new File("lecturer.txt");
File temp = new File("lectemp.txt");
old.delete();
temp.renameTo(old);

        String lectid = jLabel1.getText().trim();
        String passw = Lpass.getText().trim();
        String name = LName.getText().trim();
        String email = Lemail.getText().trim();
        //trim will make sure spaces are ignored
        File old = new File("lecturer.txt");
        File temp = new File("lectemp.txt");
        try {
            Scanner sc = new Scanner(new File("lecturer.txt")).useDelimiter(",");
            //FileWriter writer = new FileWriter("lectemp.dat", true);
            FileWriter writer = new FileWriter("lectemp.txt", true);
            BufferedWriter print = new BufferedWriter(writer);
            sc.nextLine();
            while (sc.hasNextLine()) {
                String swap = sc.nextLine(); //putting it before the while statement causes it to crash
                if(swap.contains(lectid + ",")){
                    print.newLine();
                    print.write(lectid + "," +name+ "," +passw+ "," +email);

                }else{
                    print.newLine();
                    print.write(swap);
                }               
            }
            sc.close();
            print.close();
            writer.close();
            Deletion(old,temp);

public static void Deletion(File file1, File file2){ //temp renaming with method
        if(file1.delete()){
                System.out.println("File deleted");
            }else{System.err.println("ERROR");}

            if(file2.renameTo(file1)){
                System.out.println("File renamed");
            }else{System.err.println("ERROR");}
    }

我希望输出是“lecturer.txt”被删除，“letemp.txt”被重命名为“lecturer.txt”但是，它总是以两者结束，没有任何内容被删除或重命名。当我尝试第一个代码时，它总是说未删除。

Answer 1

有时文件可能无法删除，例如，如果您没有文件的权限或文件仍处于打开状态。据我所知，操作系统本身不会阻止您删除该文件。

我建议您更改代码，不要使用

File.delete();

至

try {
    Files.delete(File.deleteToPath);
} catch (Exception e)
    System.out.println("Failed because: " + e.getMessage());
}

与"file"调用不同，"file"操作将抛出一个有用的异常，因此您实际上可以知道删除失败的原因。如果您的删除调用每次都失败，这应该可以轻松调试。

https://docs.oracle.com/javase/7/docs/api/java/nio/file/Files.html#delete(java.nio.file.Path)