《JAVA300集》IO流_檔案分割-day18
阿新 • • 發佈：2020-12-31
技術標籤：《JAVA300集》學習java檔案分割
目錄
（1）分塊讀取檔案、指定位置讀取剩餘全部內容、指定位置讀取剩餘部分內容
檔案分割
RandomAccessFile
該類的例項支援讀取和寫入隨機訪問檔案。
（1）分塊讀取檔案、指定位置讀取剩餘全部內容、指定位置讀取剩餘部分內容
package Test_IO; /* * 三種隨機讀取方法 * */ import java.io.IOException; import java.io.RandomAccessFile; import java.io.File; public class RandTest01 { public static void main(String[] args) throws IOException { //分塊讀取 String path = "D:/Java/ZhuoQiu/src/Test_IO/DataTest.java"; File src = new File(path); long allLen = src.length(); //總長度 System.out.println(allLen); int blockSize = 512; //每塊大小 int size = (int)Math.ceil(allLen*1.0/blockSize); //向上取整, 分多少塊 int beginPos = 0; //起始位置 int actualSize = (int)(blockSize>allLen?allLen:blockSize); //條件成立，執行：左邊 for(int i=0;i<size;i++){ beginPos = i*blockSize; if(i==size-1){ //最後一塊 actualSize = (int)allLen; //len剩餘量 }else{ System.out.println(i); actualSize = blockSize; allLen -=actualSize; } System.out.println("i:"+i+" begin:"+beginPos+" len:"+allLen); //完成分塊 RandomAccessFile raf = new RandomAccessFile(new File(path), "r");//r表示read raf.seek(beginPos); //操作（分段讀取） byte[] flush = new byte[1024]; //緩衝容器 int len = -1; while ((len = raf.read(flush)) != -1) { if (actualSize > len) { System.out.println(new String(flush, 0, len)); actualSize -= len; }else{ System.out.println(new String(flush, 0, actualSize)); break; } } raf.close(); } } //指定起始位置，讀取剩餘的所有內容 public static void test1() throws IOException{ String path = "D:/Java/ZhuoQiu/src/Test_IO/DataTest.java"; RandomAccessFile raf = new RandomAccessFile(new File(path),"r");//r表示read //隨機讀取 raf.seek(2);//從第二個位置開始 //讀取 //操作（分段讀取） byte[] flush = new byte[1024]; //緩衝容器 int len = -1; while((len=raf.read(flush))!=-1){ System.out.println(new String(flush,0,len)); } raf.close(); } //指定起始位置，讀取剩餘一定大小的內容 public static void test2() throws IOException { String path = "D:/Java/ZhuoQiu/src/Test_IO/DataTest.java"; RandomAccessFile raf = new RandomAccessFile(new File(path), "r");//r表示read //起始位置 int beginPos = 2; //實際大小 int actualSize = 1026; raf.seek(beginPos); //讀取 //操作（分段讀取） byte[] flush = new byte[1024]; //緩衝容器 int len = -1; while ((len = raf.read(flush)) != -1) { if (actualSize > len) { System.out.println(new String(flush, 0, len)); actualSize -= len; }else{ System.out.println(new String(flush, 0, actualSize)); break; } } raf.close(); } }
（2）同時實現讀取和寫入
import java.io.IOException; import java.io.RandomAccessFile; import java.io.File; public class RandTest02 { public static void main(String[] args) throws IOException { //分塊讀取 String path = "D:/Java/ZhuoQiu/src/Test_IO/DataTest.java"; RandomAccessFile raf = new RandomAccessFile(new File(path), "r");//r表示read RandomAccessFile raf2 = new RandomAccessFile(new File("print.txt"), "rw");//rw表示write long allLen = raf.length(); //總長度 System.out.println(allLen); int blockSize = 512; //每塊大小 int size = (int) Math.ceil(allLen * 1.0 / blockSize); //向上取整, 分多少塊 int beginPos = 0; //起始位置 int actualSize = (int) (blockSize > allLen ? allLen : blockSize); //條件成立，執行：左邊 for (int i = 0; i < size; i++) { beginPos = i * blockSize; if (i == size - 1) { //最後一塊 actualSize = (int) allLen; //len剩餘量 } else { System.out.println(i); actualSize = blockSize; allLen -= actualSize; } System.out.println("i:" + i + " begin:" + beginPos + " len:" + allLen); //完成分塊 raf.seek(beginPos); //操作（分段讀取） byte[] flush = new byte[1024]; //緩衝容器 int len = -1; while ((len = raf.read(flush)) != -1) { if (actualSize > len) { raf2.write(flush, 0, len); actualSize -= len; } else { raf2.write(flush, 0, actualSize); break; } } } raf2.close(); raf.close(); } }
（3） 用面向物件的思想封裝程式碼
（加入了檔案合併）
package Test_IO; import java.io.*; import java.util.ArrayList; import java.util.List; public class SpliteFile { //源頭 private File src; //目的地（資料夾） private String destDir; //所有分割後的檔案儲存路徑 private List<String> destPaths; //每塊大小 private int blockSize; //塊數 private int size; public SpliteFile(String srcPath, String destDir, int blockSize) { this.src = new File(srcPath); this.destDir = destDir; this.blockSize = blockSize; this.destPaths = new ArrayList<String>(); //初始化 init(); } //初始化 private void init() { long len = this.src.length(); this.size = (int) Math.ceil(len * 1.0 / blockSize); for (int i = 0; i < size; i++) { this.destPaths.add(this.destDir + "/"+ i + "-" + this.src.getName()); } } //分割 public void split() throws IOException { long allLen = src.length(); //總長度 int size = (int) Math.ceil(allLen * 1.0 / blockSize); //向上取整, 分多少塊 int beginPos = 0; //起始位置 int actualSize = (int) (blockSize > allLen ? allLen : blockSize); //條件成立，執行：左邊 for (int i = 0; i < size; i++) { beginPos = i * blockSize; if (i == size - 1) { //最後一塊 actualSize = (int) allLen; //len剩餘量 } else { System.out.println(i); actualSize = blockSize; allLen -= actualSize; } splitDetail(i,beginPos,actualSize); } } private void splitDetail(int i, int beginPos, int actualSize) throws IOException { RandomAccessFile raf = new RandomAccessFile(this.src, "r"); RandomAccessFile raf2 = new RandomAccessFile(this.destPaths.get(i), "rw"); System.out.println(this.destPaths.get(i)); // OutputStream raf2 = new FileOutputStream(this.destPaths.get(i)); raf.seek(beginPos); //操作（分段讀取） byte[] flush = new byte[1024]; //緩衝容器 int len = -1; while ((len = raf.read(flush)) != -1) { if (actualSize > len) { raf2.write(flush, 0, len); actualSize -= len; } else { raf2.write(flush, 0, actualSize); break; } } raf2.close(); raf.close(); } public void merge(String destPath) throws IOException { //輸出流 OutputStream os = new BufferedOutputStream(new FileOutputStream(destPath,true)); //輸入流 for(int i =0;i<destPaths.size();i++){ InputStream is = new BufferedInputStream(new FileInputStream(destPaths.get(i))); //拷貝 byte[] flush = new byte[1024]; int len = -1; while((len=is.read(flush))!=-1){ os.write(flush,0,len); } os.flush(); is.close(); } os.close(); } public static void main(String[] args) throws IOException { String srcPath = "D:/Java/ZhuoQiu/src/Test_IO/DataTest.java"; String destDir = "D:/Java/ZhuoQiu/src/dest"; SpliteFile sf = new SpliteFile(srcPath, destDir, 1024); sf.split(); } }