java文件复制代码片断(java实现文件拷贝)

Java文件复制是Java中常用的操作之一，我们通常利用类库中的FileInputStream 和 FileOutputStream来实现文件拷贝。下面是Java文件复制代码片段的完整攻略：

步骤一：创建输入输出流对象

首先要创建输入输出流对象，读取原文件并将文件写入指定文件。这里我们使用Java中的FileInputStream和FileOutputStream。

FileInputStream inStream = new FileInputStream("sourceFile.txt");
FileOutputStream outStream = new FileOutputStream("targetFile.txt");

步骤二：读取输入流

读取源文件中的数据并将其保存在字节数组中。以下是将源文件中的数据读入字节数组的示例：

byte[] buffer = new byte[1024];
int length;
while ((length = inStream.read(buffer)) > 0) {
    outStream.write(buffer, 0, length);
}

这段代码将原文件中的数据读入buffer中，直到数据读取到末尾。然后通过write方法将数据写入到targetFile.txt中。

步骤三：关闭输入输出流

复制完文件之后，可以将流关闭以释放其资源。以下是关闭流的示例：

inStream.close();
outStream.close();

完整的Java代码如下：

import java.io.*;

public class FileCopyDemo {
  public static void main(String[] args) throws IOException {
    FileInputStream inStream = null;
    FileOutputStream outStream = null;
    try {
        File inputFile = new File("sourceFile.txt");
        File outputFile = new File("targetFile.txt");

        inStream = new FileInputStream(inputFile);
        outStream = new FileOutputStream(outputFile);

        byte[] buffer = new byte[1024];
        int length;
        while ((length = inStream.read(buffer)) > 0) {
            outStream.write(buffer, 0, length);
        }
    } finally {
        if (inStream != null) inStream.close();
        if (outStream != null) outStream.close();
    }
  }
}

示例1：将当前文件夹下名为source.png的图片文件复制到当前文件夹下的target.png文件中。

import java.io.*;

public class FileCopyDemo {
  public static void main(String[] args) throws IOException {
    FileInputStream inStream = null;
    FileOutputStream outStream = null;
    try {
        File inputFile = new File("source.png");
        File outputFile = new File("target.png");

        inStream = new FileInputStream(inputFile);
        outStream = new FileOutputStream(outputFile);

        byte[] buffer = new byte[1024];
        int length;
        while ((length = inStream.read(buffer)) > 0) {
            outStream.write(buffer, 0, length);
        }
    } finally {
        if (inStream != null) inStream.close();
        if (outStream != null) outStream.close();
    }
  }
}

示例2：将当前文件夹下的名为source.txt的文件复制到当前文件夹下的target.txt文件中。

import java.io.*;

public class FileCopyDemo {
  public static void main(String[] args) throws IOException {
    FileInputStream inStream = null;
    FileOutputStream outStream = null;
    try {
        File inputFile = new File("source.txt");
        File outputFile = new File("target.txt");

        inStream = new FileInputStream(inputFile);
        outStream = new FileOutputStream(outputFile);

        byte[] buffer = new byte[1024];
        int length;
        while ((length = inStream.read(buffer)) > 0) {
            outStream.write(buffer, 0, length);
        }
    } finally {
        if (inStream != null) inStream.close();
        if (outStream != null) outStream.close();
    }
  }
}

以上两个示例都遵循了Java文件复制的完整流程，可以更改文件名和路径实现更多的文件复制操作。