本文实例为大家分享了Java实现文件的分割与合并的具体代码，供大家参考，具体内容如下
一、文件分割实现思想
1、设置分割文件（块）的大小；
2、通过输入流获取源文件的大小；
3、根据1、2步的计算结果计算出分割后的文件个数（源文件的大小 / 设置分割文件的大小 ，如果设置的文件大小大于源文件的大小，接下来判断1、2步计算结果，如果余数为0，则文件个数为商值，如果余数大于0，则文件个数为商值加1。
如果设置分割文件的大小小于源文件的大小，那么文件个数为1。）；
4、分割文件（边读边写）。
二、文件合并实现思想
1、文件合并与文件分割实现思想的第4步类似，就是边读边写。
方式一：调用API中的RandomAccessFile，此类的实例支持对随机存取文件的读取和写入。按块分割与合并，示例代码如下：
package com.cn.filesplite1;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.io.SequenceInputStream;
import java.util.ArrayList;
import java.util.List;
import java.util.Vector;
public class SplitFile {
//文件的路径
private String filePath;
//文件名
private String fileName;
//文件大小
private long length;
//块数
private int size;
//每块的大小
private long blockSize;
//分割后的存放目录
private String destBlockPath;
//每块的名称
private List<String> blockPath;
public SplitFile(){
blockPath = new ArrayList<String>();
}
public SplitFile(String filePath,String destBlockPath){
this(filePath,destBlockPath,1024);
}
public SplitFile(String filePath,String destBlockPath,long blockSize){
this();
this.filePath= filePath;
this.destBlockPath =destBlockPath;
this.blockSize=blockSize;
init();
}
public void init(){
File src =null;
//健壮性
if(null==filePath ||!(((src=new File(filePath)).exists()))){
return;
}
if(src.isDirectory()){
return ;
}
//文件名
this.fileName =src.getName();
//计算块数 实际大小 与每块大小
this.length = src.length();
//修正 每块大小
if(this.blockSize>length){
this.blockSize =length;
}
//确定块数
size= (int)(Math.ceil(length*1.0/this.blockSize));
//确定文件的路径
initPathName();
}
private void initPathName(){
for(int i=0;i<size;i++){
this.blockPath.add(destBlockPath+"/"+this.fileName+".part"+i);
}
}
public void split(){
long beginPos =0; //起始点
long actualBlockSize =blockSize; //实际大小
//计算所有块的大小、位置、索引
for(int i=0;i<size;i++){
if(i==size-1){ //最后一块
actualBlockSize =this.length-beginPos;
}
spiltDetail(i,beginPos,actualBlockSize);
beginPos+=actualBlockSize; //本次的终点，下一次的起点
}
}
private void spiltDetail(int idx,long beginPos,long actualBlockSize){
//1、创建源
File src = new File(this.filePath); //源文件
File dest = new File(this.blockPath.get(idx)); //目标文件
//2、选择流
RandomAccessFile raf = null; //输入流
BufferedOutputStream bos=null; //输出流
try {
raf=new RandomAccessFile(src,"r");
bos =new BufferedOutputStream(new FileOutputStream(dest));
//读取文件
raf.seek(beginPos);
//缓冲区
byte[] flush = new byte[1024];
//接收长度
int len =0;
while(-1!=(len=raf.read(flush))){
if(actualBlockSize-len>=0){ //查看是否足够
//写出
bos.write(flush, 0, len);
actualBlockSize-=len; //剩余量
}else{ //写出最后一次的剩余量
bos.write(flush, 0, (int)actualBlockSize);
break;
}
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}finally{
FileUtil.close(bos,raf);
}
}
public void merge(String destPath){
//创建源
File dest =new File(destPath);
//选择流
BufferedOutputStream bos=null; //输出流
SequenceInputStream sis =null ;//输入流
//创建一个容器
Vector<InputStream> vi = new Vector<InputStream>();
try {
for (int i = 0; i < this.blockPath.size(); i++) {
vi.add(new BufferedInputStream(new FileInputStream(new File(this.blockPath.get(i)))));
}
bos =new BufferedOutputStream(new FileOutputStream(dest,true)); //追加
sis=new SequenceInputStream(vi.elements());
//缓冲区
byte[] flush = new byte[1024];
//接收长度
int len =0;
while(-1!=(len=sis.read(flush))){
bos.write(flush, 0, len);
}
bos.flush();
FileUtil.close(sis);
} catch (Exception e) {
}finally{
FileUtil.close(bos);
}
}
public static void main(String[] args) {
//1024 * 30 表示按照每块30Kb大小分割
SplitFile split = new SplitFile("F:/123/1234/logFile.txt","F:/123/",1024 * 30);
System.out.println(split.size);
// split.split();
split.merge("F:/123/logFile.txt");
}
}
package com.cn.filesplite1;
import java.io.Closeable;
public class FileUtil {
public static void close(Closeable ... io){
for(Closeable temp:io){
try {
if (null != temp) {
temp.close();
}
} catch (Exception e) {
}
}
}
public static <T extends Closeable> void closeAll(T ... io){
for(Closeable temp:io){
try {
if (null != temp) {
temp.close();
}
} catch (Exception e) {
}
}
}
}方式二：用读写的方式实现文件的分割与合并，具体实现如下代码所示：
定义一个抽象类
package com.cn.filesplite2;
import java.io.File;
import java.io.IOException;
public abstract class SplitFile {
public static long MAX_BYTE = 1024 * 1024 * 1024 * 2L; //2G
public abstract int getSplitFileNum(long fileByte,String fileParh);
public abstract long getFileLength(File file) ;
public abstract String[] splitFile (File srcFile,int splitFileNum) throws IOException;
public abstract void mergeFile(String[] files,String newFile) throws IOException;
}实现类
package com.cn.filesplite2;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
public class SplitTextFile extends SplitFile{
@Override
public long getFileLength(File file) {
FileReader fr = null;
BufferedReader br = null;
//文件大小
long fileSize = 0;
try {
fr = new FileReader(file);
br = new BufferedReader(fr);
String line = br.readLine();
//按行读取文件
while(line != null){
//计算文件大小
fileSize += line.length();
line = br.readLine();
}
} catch (IOException e) {
e.printStackTrace();
}finally{
//关闭输入流
try {
if(br != null){
br.close();
}
if(fr != null){
fr.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
//返回文件大小
return fileSize;
}
@Override
public int getSplitFileNum(long fileByte,String fileParh){
fileByte = getFileLength(new File(fileParh));
if(MAX_BYTE < fileByte){
if(fileByte % MAX_BYTE == 0){
return (int) (fileByte/MAX_BYTE);
}else{
return (int) (fileByte/MAX_BYTE) + 1;
}
}
return 1;
}
@Override
public String[] splitFile(File srcFile, int splitFileNum) throws IOException {
splitFileNum = getSplitFileNum(getFileLength(srcFile), srcFile.toString());
if(splitFileNum <= 0){
return null;
}
FileReader fr = null;
BufferedReader br = null;
long readNum = 0;
String[] splits = new String[splitFileNum];
try {
fr = new FileReader(srcFile);
br = new BufferedReader(fr);
int i = 0;
while(splitFileNum > i){
//分割后的文件名
String name = null;
//文件后缀
String nameLast = null;
if(srcFile.getName().indexOf(".") != -1){
name = srcFile.getName().substring(0, srcFile.getName().indexOf("."));
int last = srcFile.getName().lastIndexOf(".");
// System.out.println(i);
// String string = str.substring(i);
nameLast = srcFile.getName().substring(last);
}else{
name = srcFile.getName();
}
splits[i] = srcFile.getParent() + "/" + name + "_" + i + nameLast;
File wfile = new File(splits[i]);
if(!wfile.exists()){
wfile.getParentFile().mkdirs();
wfile.createNewFile();
}
FileWriter fw = new FileWriter(wfile,false);
BufferedWriter bw = new BufferedWriter(fw);
String line = br.readLine();
int flush = 0;
while(line != null){
if(line.trim().length() == 0){
line = br.readLine();
continue;
}
readNum += line.length();
if(i + 1 == splitFileNum){
bw.write(line);
bw.newLine();
}else{
if(readNum >= MAX_BYTE){
bw.write(line);
bw.newLine();
break;
}else{
bw.write(line);
bw.newLine();
}
}
line = br.readLine();
if(flush % 100 == 0){
bw.flush();
}
}
bw.flush();
fw.flush();
bw.close();
fw.close();
readNum = 0;
i++;
}
} catch (RuntimeException e) {
e.printStackTrace();
}
finally{
try {
if(br != null) br.close();
if(fr != null) fr.close();
} catch (Exception e) {
e.printStackTrace();
}finally{
br = null;
fr = null;
}
}
return splits;
}
@Override
public void mergeFile(String[] files, String newFile) throws IOException {
File wfile = new File(newFile);
FileWriter writer = null;
BufferedWriter bufferedWriter = null;
try {
writer = new FileWriter(wfile,false);
bufferedWriter = new BufferedWriter(writer);
for(int i = 0; i < files.length; i++){
File rFile = new File(files[i]);
FileReader reader = new FileReader(rFile);
BufferedReader bufferedReader = new BufferedReader(reader);
String line = bufferedReader.readLine();
while(line != null){
if(line.trim().length() == 0){
line = bufferedReader.readLine();
continue;
}
bufferedWriter.write(line);
bufferedWriter.newLine();
line = bufferedReader.readLine();
}
}
bufferedWriter.flush();
writer.flush();
} catch (Exception e) {
e.printStackTrace();
}finally{
if(bufferedWriter != null)
bufferedWriter.close();
bufferedWriter = null;
if(writer != null)
writer.close();
writer = null;
}
}
}测试类
package com.cn.filesplite2;
import java.io.File;
import java.io.IOException;
import org.junit.Test;
public class TestSplitFile {
SplitTextFile splitTextFile = new SplitTextFile();
@Test
public void funSplitFile() throws IOException{
String srcPath = "E:/splitfile/splitfile.txt";
File file = new File(srcPath);
long fileLength = splitTextFile.getFileLength(file);
System.out.println("文件大小：" + fileLength);
int partitionFileNum = splitTextFile.getSplitFileNum(fileLength, srcPath);
System.out.println("个数" + partitionFileNum);
//文件分割
splitTextFile.splitFile(new File(srcPath), partitionFileNum);
}
@Test
public void funMergeFile() throws IOException{
String[] files = {"E:/splitfile/splitfile0",
"E:/splitfile/splitfile1",
"E:/splitfile/splitfile2"
// ...files/
};
String newFile = "E:/splitfile/newmergefile";
splitTextFile.mergeFile(files, newFile);
}
}以上内容如有任何问题或错误，恳请大家能给予意见，我会及时更正，谢谢大家。
本文的全部内容介绍完了，希望对大家的学习有所帮助，也希望大家多多支持编程网。
