使用FileInputStream從一個文件讀取並使用FileOutputStream寫入另一個文件

Question

我試圖使用title中指定的類從一個文件讀取並將寫入的字節寫入另一個文件。我成功做到了，但是當我嘗試嘗試不同的事情時遇到了一個我不理解的問題。

這是代碼

import java.io.*;
public class FileInputStreamDemo {

    public static void main(String[] args)
            throws Exception {
        // TODO Auto-generated method stub
        int size;
        InputStream f = new
                FileInputStream("G:/Eclipse Workspace/FileInputStream Demo/src/FileInputStreamDemo.java");

        System.out.println("Total available bytes: " + (size = f.available()));
    /*int n=size/40;
    System.out.println("first " + n + " bytes of file one read() at a time");

    for (int i=0;i<n;i++)
    {
        System.out.print((char) f.read());
    }
    System.out.println("\n Still available: " + f.available());
    System.out.println("reading the next" + n + "with one read(b[])");
    byte b[] = new byte[n]; */
    /*for(int i=0;i<size;i++)
    {
        System.out.print((char) f.read());
    }*/
        OutputStream f1 = new
                FileOutputStream("G:/Eclipse Workspace/FileInputStream Demo/test.txt");
        for (int count = 0; count < size; count++) {
            f1.write(f.read());
        }
        for (int i = 0; i < size; i++) {
            System.out.print(f.read());
        }

        f.close();
        f1.close();
    }
}

我正在談論的問題是，當我第一次從FileInputStream對象f即f.read()讀取並將其寫入f1即FileOutputStream對象時，它會繼續執行其應做的工作，但是當我嘗試執行再次讀取它返回-1。 為什么這樣 ？

Answer 1

首先使用RandomAccessFile和seek(0)方法返回。

RandomAccessFile file = new RandomAccessFile(new File("G:/Eclipse Workspace/FileInputStream Demo/src/FileInputStreamDemo.java"), "r");

這是示例代碼：

import java.io.File;
import java.io.FileOutputStream;
import java.io.OutputStream;
import java.io.RandomAccessFile;

public class FileInputStreamDemo {

    public static void main(String[] args) throws Exception {
        long size;
        File file = new File("D:/Workspace/JavaProject/src/com/test/FileInputStreamDemo.java");
        RandomAccessFile f = new RandomAccessFile(file, "r");

        System.out.println("Total available bytes: " + (size = file.length()));
        OutputStream f1 = new FileOutputStream(new File(
                "D:/Workspace/JavaProject/resources/test.txt"));
        for (int count = 0; count < size; count++) {
            f1.write(f.read());
        }
        f.seek(0);
        for (int i = 0; i < size; i++) {
            System.out.print((char)f.read());
        }

        f.close();
        f1.close();
    }
}