RandomAccessFile 类读写测试及其性能优化(2)
RandomAccessFile 类读写测试及其性能优化(二)
package io; import java.io.File; import java.io.RandomAccessFile; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; /** * RandomAccessFile 类读写测试及其性能优化(二) * * 读取 RandomAccessFile 类读写测试及其性能优化(一) * (链接 http://jackyin5918.iteye.com/blog/2022888 )中 * GenerateIntArray 生成的并保存到文件的数据. * * 多线程读取文件和多线程写文件一样没有提升速度. * * 疑似RandomAccessFile 读写文件时会阻塞,对文件加锁神马的的,待研究. * * @author 10106511 * */ public class GetTheMiddle { private int count = 1000; // 数组的个数, private int size = 10; // 每个数组的元素个数 private int[][] dataArr; public GetTheMiddle() { dataArr = new int[count][size]; } public GetTheMiddle(int count, int size) { this.count = count; this.size = size; this.dataArr = new int[count][size]; } public int[][] getDataArr() { return dataArr; } public int[][] readData(File f) { try { RandomAccessFile rf = new RandomAccessFile(f, "r"); for (int i = 0; i < count; i++) { for (int j = 0; j < size; j++) { dataArr[i][j] = rf.readInt(); } } rf.close(); } catch (Exception e) { e.printStackTrace(); } return dataArr; } class ReadDataTask implements Runnable { private File f; private int dataIndex; public ReadDataTask(File f,int dataIndex) { this.f = f; this.dataIndex = dataIndex; } @Override public void run() { try { RandomAccessFile rf = new RandomAccessFile(f, "r"); rf.skipBytes(dataIndex * size * 4 ); for (int j = 0; j < size; j++) { dataArr[dataIndex][j] = rf.readInt(); } rf.close(); } catch (Exception e) { e.printStackTrace(); } } } public int[][] readData_M(File f) { try { ExecutorService exec = Executors.newCachedThreadPool(); for(int i=0;i<count;i++) { exec.execute(new ReadDataTask(f,i)); } exec.shutdown(); while(true) { if(exec.isTerminated()) break; } } catch (Exception e) { e.printStackTrace(); } return dataArr; } public static void main(String[] args) { int count = 3; int size = 4; boolean bPrintData = true; // 是否打印生成的数组,当数据量大是不打印,只在小数据量时打印以便测试 System.out.printf("count = %d, size = %d \n\n", count, size); GenerateIntArray generator = new GenerateIntArray(count, size); GetTheMiddle gm = new GetTheMiddle(count,size); File f; try { f = new File("D:\\D\\test_data.dat"); generator.refreshDataArr(); generator.writeData2File_B(f); System.out.println("正在读取数据,请稍后..."); long startTmie = System.nanoTime(); gm.readData(f); long totalTime = (System.nanoTime() - startTmie)/ 100000; System.out.println("readData(f) 读取数据成功, 耗时:" + totalTime); System.out.println(); System.out.println("正在读取数据,请稍后..."); startTmie = System.nanoTime(); gm.readData_M(f); totalTime = (System.nanoTime() - startTmie)/ 100000; System.out.println("readData_M(f) 读取数据成功, 耗时:" + totalTime); System.out.println(); } catch (Exception e) { e.printStackTrace(); } if(bPrintData) { System.out.println("generator中生成的数据..."); int[][] intArr = generator.getDataArr(); for (int i = 0; i < count; i++) { for (int j = 0; j < size; j++) { System.out.printf("%d ", intArr[i][j]); } System.out.println(); } System.out.println("读取出来的数组..."); intArr = gm.getDataArr(); for (int i = 0; i < count; i++) { for (int j = 0; j < size; j++) { System.out.printf("%d ", intArr[i][j]); } System.out.println(); } } } }