Attempts to copy the first 'amount' bytes of file 'src' to 'dst', returning the number of bytes actually copied. - Java File Path IO

Java examples for File Path IO:File Copy

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Description

Attempts to copy the first 'amount' bytes of file 'src' to 'dst', returning the number of bytes actually copied.

Demo Code


//package com.java2s;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

public class Main {
    public static void main(String[] argv) throws Exception {
        File src = new File("Main.java");
        File dst = new File("Main.java");
        System.out.println(copy(src, dst));
    }/* www.jav  a2s .  c  om*/

    /** 
     * Attempts to copy the first 'amount' bytes of file 'src' to 'dst',
     * returning the number of bytes actually copied.  If 'dst' already exists,
     * the copy may or may not succeed.
     * 
     * @param src the source file to copy
     * @param amount the amount of src to copy, in bytes
     * @param dst the place to copy the file
     * @return the number of bytes actually copied.  Returns 'amount' if the
     *  entire requested range was copied.
     */
    public static int copy(File src, int amount, File dst) {
        final int BUFFER_SIZE = 1024;
        int amountToRead = amount;
        InputStream in = null;
        OutputStream out = null;
        try {
            //I'm not sure whether buffering is needed here.  It can't hurt.
            in = new BufferedInputStream(new FileInputStream(src));
            out = new BufferedOutputStream(new FileOutputStream(dst));
            byte[] buf = new byte[BUFFER_SIZE];
            while (amountToRead > 0) {
                int read = in.read(buf, 0,
                        Math.min(BUFFER_SIZE, amountToRead));
                if (read == -1)
                    break;
                amountToRead -= read;
                out.write(buf, 0, read);
            }
        } catch (IOException e) {
        } finally {
            if (in != null)
                try {
                    in.close();
                } catch (IOException e) {
                }
            if (out != null) {
                try {
                    out.flush();
                } catch (IOException e) {
                }
                try {
                    out.close();
                } catch (IOException e) {
                }
            }
        }
        return amount - amountToRead;
    }

    /** 
     * Copies the file 'src' to 'dst', returning true iff the copy succeeded.
     * If 'dst' already exists, the copy may or may not succeed.  May also
     * fail for VERY large source files.
     */
    public static boolean copy(File src, File dst) {
        //Downcasting length can result in a sign change, causing
        //copy(File,int,File) to terminate immediately.
        long length = src.length();
        return copy(src, (int) length, dst) == length;
    }
}

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