寫出到控制台以及文件

Question

我試圖讓我的java程序的輸出寫入文件。

用戶輸入一些不應包含在文件中的數據。 當程序響應它應該輸出信息給用戶，並承擔全部輸出寫入到文件中。

從示例開始，我在驅動程序類的頂部開始：

static BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
static String lineFromOutput;

這段代碼在我可能從程序接收輸出的每個地方：

try {
    lineFromInput = in.readLine();
    FileWrite.write(lineFromInput);
} catch (IOException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
}

而它的主叫是：

public class FileWrite {
    public static void write(String message) { 
        PrintWriter out = null;
        try {
            out = new PrintWriter(new FileWriter("output.txt"), true);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        out.write(message);
        out.close();
    }
}

它會創建輸出文件，但就是這樣。 程序的輸出都沒有寫入。 我已經查看了很多例子，這似乎是最簡單的方法，盡管我對任何其他建議持開放態度。

謝謝！

Answer 1

每次寫入調用都會打開和關閉文本文件。 每次打開它都會被覆蓋，所以我希望只寫下最后一件事就會出現在文件中。

我建議從構造函數中打開輸出文件，然后從close方法關閉它。

Answer 2

我認為它應該是InputStremReader ，下面是單個t語句：

static BufferedReader in= new BufferedReader(new OutputtStreamReader(System.in));
static String lineFromOutput;

如

static BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
static String lineFromOutput;

編輯：這很好。 請確保通過輸入控制台提供輸入。 另請注意，它只讀取和寫入（覆蓋）單行。

    public class FileWrite {
       public static void write(String message) { 
                PrintWriter out = null;
              try {
                  out = new PrintWriter(new FileWriter("output.txt"), true);
              } catch (IOException e) {
                  // TODO Auto-generated catch block
                  e.printStackTrace();
              }
                out.write(message);
                out.close();
        }

       public static void main(String[] args){
           String lineFromInput;
           try {
                BufferedReader in = new BufferedReader(
                                            new InputStreamReader(System.in));
                lineFromInput = in.readLine();
                FileWrite.write(lineFromInput);
                in.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
           }
       }
     }

編輯2：更新了多線輸入程序。 它不是每次寫入時打開和關閉文件的最佳方式，但我只是試圖讓您的程序稍作修改。 請告訴我，如果您需要建議以避免重復打開/關閉輸出文件。

更改亮點：

1. 在輸入中接收讀取行直到“退出”（根據需要改變單詞）

2. 以append模式打開文件。

    public class FileWrite { public static void write(String message) { PrintWriter out = null; try { out = new PrintWriter(new FileWriter("output.txt", true), true); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } out.write(message); out.close(); } public static void main(String[] args){ String lineFromInput = ""; try { System.out.println("Provide the inputs in any number of lines"); System.out.println("Type \\"exit\\" in new line when done"); BufferedReader in = new BufferedReader( new InputStreamReader(System.in)); while(!"exit".equals(lineFromInput)){ lineFromInput = in.readLine(); FileWrite.write(lineFromInput+System.lineSeparator()); } in.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } 

EDIT3：使用Scanner讀取輸入的更新程序：

        private static HashMap<Integer, Object> shapes = 
                                              new HashMap<Integer, Object>();
        static int i = 0;

        public static void main(String[] args) {
            PrintWriter output = null;
            Scanner scanner = new Scanner(System.in);
            try {
                output = new PrintWriter(new FileWriter("output.txt"), true);
            } catch (IOException e1) {
                System.err.println("You don't have accress to this file");
                System.exit(1);
            }
            String command = "";
            while(!"quit".equalsIgnoreCase(command)){
                System.out.println("Enter your Command: ");
                command = scanner.next();
                if (command.equalsIgnoreCase("create")) {
                    String type = scanner.next();
                    if (type.equalsIgnoreCase("line")) {
                        double length = scanner.nextDouble();
                        Line l = new Line(length);
                        scanner.nextLine();//flush the previous line
                        String line = scanner.nextLine();
                        output.format("%s", line);
                        shapes.put(i, l);
                        i++;
                    }else if (type.equalsIgnoreCase("circle")) {
                        double radius = scanner.nextDouble();
                        String color = scanner.next();
                        Circle c = new Circle(radius, Colors.valueOf(color));
                        scanner.nextLine();//flush the previous line
                        String line = scanner.nextLine();
                        output.format("%s", line);
                        shapes.put(i, c);
                        i++;
                    }else if (type.equals("rectangle")) {
                        double length = scanner.nextDouble();
                        double width = scanner.nextDouble();
                        String color = scanner.next();
                        Rectangle r = new Rectangle(length, width,
                        Colors.valueOf(color));
                        scanner.nextLine();//flush the previous line
                        String line = scanner.nextLine();
                        output.format("%s", line);
                        shapes.put(i, r);
                        i++;
                    }else if (type.equals("square")) {
                        double length = scanner.nextDouble();
                        String color = scanner.next();
                        Square s = new Square(length, Colors.valueOf(color));
                        scanner.nextLine();//flush the previous line
                        String line = scanner.nextLine();
                        output.format("%s", line);
                        shapes.put(i, s);
                        i++;
                    }
                }else if (command.equals("printbyperimeter")) {
                    Shape[] shapeArray = shapes.values().toArray(new Shape[0]);
                    Arrays.sort(shapeArray);
                            System.out.println("Print in ascending order...");
                    for (int j = 0; j < shapeArray.length; j++) {
                        Shape temp = shapeArray[j];
                        if (temp.getClass().getName().equals("Line")) {
                            System.out.println("Shape: " 
                                    + temp.getClass().getName() + ", Perimeter: "
                                    + temp.getPerimeter());
                                } else {
                            System.out.println("Shape: " 
                                    + temp.getClass().getName() + ", Color: "
                                    + ((Colorable) temp).getColor()
                                    + ", Perimeter: " + temp.getPerimeter());
                                }
                            }
                }else if (command.equals("printbyarea")) {
                    Shape[] shapeArray = shapes.values().toArray(new Shape[0]);
                    System.out.println("Print in random order...");
                    for (int j = 0; j < shapeArray.length; j++) {
                        Shape temp = shapeArray[j];
                        if (!temp.getClass().getName().equals("Line")) {
                            System.out.println("Shape: "
                                    + temp.getClass().getName() + ", Color: "
                                    + ((Colorable) temp).getColor() + ", Area: "
                                    + ((Areable) temp).getArea());
                                }
                        }
                }else if (command.equals("quit")) {
                    scanner.close();
                    System.exit(0);
                }
           }
           output.close();
        }

Answer 3

嘗試使用代碼。 這個對我有用。 您只需要更改文件路徑以匹配您希望輸出的位置。 我在這里使用BufferedWriter，我認為是首選。

public static void main(String[] args) {
BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
String lineFromOutput;

try {
    lineFromOutput = in.readLine();
    FileWrite.write(lineFromOutput);
} catch (IOException e) {
// TODO Auto-generated catch block
 e.printStackTrace();
}



}

public static class FileWrite {
    private static void write(String message) throws IOException { 
      BufferedWriter out = null;
    try {
        out = new BufferedWriter(new FileWriter(new File("C:\\Users\\Teresa\\Dropbox\\output.txt")));
        //Replace the above line with your path.
        out.write(message);
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
      out.close();
    }
}