Code Example of Java IO Stream Splitting a File into Multiple Subfiles

File splitting and merging is a common requirement, for example: when uploading large files, you can first split them into small blocks, upload them to the server, and then merge them. Many high-end distributed file systems (such as Google's GFS, Taobao's TFS) also split or merge files by block.

Let's take a look at the basic idea:

If there is a large file, after specifying the split size (for example: by1M cutting)

step 1:

First, calculate the final number of split small files N based on the size of the original file and the split size

step 2:

Create these N small files on the disk

step 3:

Start multiple threads (thread count = number of split files), in each thread, use the seek function of RandomAccessFile to position the read pointer to the beginning of each segment in the original file, then read the specified size forward (that is: the size of the split block), and finally write to the corresponding split file. Because of the parallel processing of multiple threads, each writes to its own small file, which is relatively fast in terms of speed.

Nachfolgender Code teilt eine Datei in mehrere Unterdateien auf, wobei jede Datei eine Größe von}}100K

package testIO;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.util.Arrays;
public class subStream {
	public static void main(String[] args) {
		//Lesen Sie zunächst die Quelldatei in den Speicher 
		int eachSize=100*1024;
		File srcFile =new File("F:",/test/test.txt");
		//Erstellen Sie ein Dateiobjekt 
		splitFile(srcFile,eachSize);
	}
	public static void splitFile(File srcFile,int eachSize){
		//Prüfen Sie, ob die Datei den Anforderungen für die Aufteilung entspricht 
		if(srcFile.length()==0){
			throw new RuntimeException("Die Datei entspricht nicht den Anforderungen für die Aufteilung");
		}
		byte[] fileContent= new byte[(int) srcFile.length()];
		try {
			//Lesen Sie den Dateiinhalt in den Speicher 
			FileInputStream fis=new FileInputStream(srcFile);
			fis.read(fileContent);
			fis.close();
		}
		catch (Exception e) {
			e.printStackTrace();
		}
		//Berechnen Sie, wie viele Teile der Datei gesplittet werden müssen 
		int fileNumber;
		if(fileContent.length%eachSize==0){
			fileNumber = fileContent.length/eachSize;
		} else{
			fileNumber = fileContent.length/eachSize+1;
		}
		for (int i=0;i<fileNumber;i++){
			String fileName = srcFile.getName()+"-"+i+".txt";
			File fi = new File(srcFile.getParent(), fileName);
			//在当前文件路径下创建拆分的文件 
			byte[] eachContent;
			//将源文件内容复制到拆分的文件中 
			if(i!=fileNumber-1){
				eachContent = Arrays.copyOfRange(fileContent, eachSize*i, eachSize*(i+1));
			} else{
				eachContent = Arrays.copyOfRange(fileContent, eachSize*i, fileContent.length);
			}
			try {
				FileOutputStream fos = new FileOutputStream(fi);
				fos.write(eachContent);
				fos.close();
				System.out.printf("输出子文件 %s,其大小是 %d,每个的大小是%d\n",fi.getAbsoluteFile(),fi.length(),eachContent.length);
			}
			catch (Exception e) {
				// 待处理：处理异常 
				e.printStackTrace();
			}
		}
	}
}

总结

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