Java NIO通道之間的數(shù)據(jù)傳輸

在Java NIO中，可以非常頻繁地將數(shù)據(jù)從一個(gè)通道傳輸?shù)搅硪粋€(gè)通道。批量傳輸文件數(shù)據(jù)是非常普遍的，因?yàn)閹讉€(gè)優(yōu)化方法已經(jīng)添加到FileChannel類(lèi)中，使其更有效率。

通道之間的數(shù)據(jù)傳輸在FileChannel類(lèi)中的兩種方法是：

• FileChannel.transferTo()方法
• FileChannel.transferFrom()方法

FileChannel.transferTo()方法

transferTo()方法用來(lái)從FileChannel到其他通道的數(shù)據(jù)傳輸。

下面來(lái)看一下transferTo()方法的例子：

public abstract class Channel extends AbstractChannel  
{    
   public abstract long transferTo (long position, long count, WritableByteChannel target);  
}

FileChannel.transferFrom()方法

transferFrom()方法允許從源通道到FileChannel的數(shù)據(jù)傳輸。

下面來(lái)看看transferFrom()方法的例子：

public abstract class Channel extends AbstractChannel  
{    
    public abstract long transferFrom (ReadableByteChannel src, long position, long count);  
}

基本通道到通道數(shù)據(jù)傳輸示例

下面來(lái)看看從4個(gè)不同文件讀取文件內(nèi)容的簡(jiǎn)單示例，并將它們的組合輸出寫(xiě)入第五個(gè)文件：

package com.yiibai;

import java.io.File;
import java.io.FileOutputStream;
import java.io.FileInputStream;
import java.nio.channels.WritableByteChannel;
import java.nio.channels.FileChannel;

public class TransferDemo {
    public static void main(String[] argv) throws Exception {
        String relativelyPath = System.getProperty("user.dir");
        // Path of Input files
        String[] iF = new String[] { relativelyPath + "/input1.txt", relativelyPath + "/input2.txt",
                relativelyPath + "/input3.txt", relativelyPath + "/input4.txt" };
        // Path of Output file and contents will be written in this file
        String oF = relativelyPath + "/combine_output.txt";
        // Acquired the channel for output file
        FileOutputStream output = new FileOutputStream(new File(oF));
        WritableByteChannel targetChannel = output.getChannel();
        for (int j = 0; j < iF.length; j++) {
            // Get the channel for input files
            FileInputStream input = new FileInputStream(iF[j]);
            FileChannel inputChannel = input.getChannel();

            // The data is tranfer from input channel to output channel
            inputChannel.transferTo(0, inputChannel.size(), targetChannel);

            // close an input channel
            inputChannel.close();
            input.close();
        }
        // close the target channel
        targetChannel.close();
        output.close();
        System.out.println("All jobs done...");
    }
}

在上述程序中，將4個(gè)不同的文件(即input1.txt，input2.txt，input3.txt和input4.txt)的內(nèi)容讀取并將其組合的輸出寫(xiě)入第五個(gè)文件，即：combine_output.txt文件的中。combine_output.txt文件的內(nèi)容如下 -

this is content from input1.txt
this is content from input2.txt
this is content from input3.txt
this is content from input4.txt