文件排序
前提：
* 文件排序
* 文件中每行保存一个数字
* 数字没有重复的
* 没有其他相关的信息与数字想关联
* 大概只有1M的内存空间可以使用
代码
package com.wutianyi.interesting;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
/**
* @author hanjie.wuhj
* 文件排序
* 文件中每行保存一个数字
* 数字没有重复的
* 没有其他相关的信息与数字想关联
* 大概只有1M的内存空间可以使用
*/
public class FileSort {
/**
* 1MB的内存
*/
byte[] results = new byte[1024 * 1024];
byte[] values = new byte[] { 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, -128 };
void createSortFile(String file) {
PrintWriter pw = null;
try {
pw = new PrintWriter(new File(file));
int value = 1024 * 1024 * 8 - 1;
for (int i = value; i >= 0; i--) {
pw.println(i);
}
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
if (null != pw) {
pw.close();
}
}
}
void sortFile(String file) {
BufferedReader reader = null;
try {
reader = new BufferedReader(new InputStreamReader(
new FileInputStream(file)));
String line = reader.readLine();
while (null != line && !line.isEmpty()) {
int v = Integer.parseInt(line);
dealValue(v);
line = reader.readLine();
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (null != reader) {
try {
reader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
void dealValue(int v) {
int index = v / 8;
int position = v % 8;
results[index] = (byte) (results[index] | values[position]);
}
void printValue(String out) {
PrintWriter pw = null;
try {
pw = new PrintWriter(new File(out));
int i = 0;
int index = 1;
for (byte result : results) {
for (int j = 0; j < 8; j++) {
if ((result & values[j]) == values[j]) {
pw.println(i + j);
}
}
i = index * 8;
++index;
}
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
if (null != pw) {
pw.flush();
pw.close();
}
}
}
public static void main(String[] args) {
FileSort sort = new FileSort();
// sort.createSortFile("sort=original.txt");
long start = System.currentTimeMillis();
sort.sortFile("sort=original.txt");
long end_1 = System.currentTimeMillis();
System.out.println("sort time: " + (end_1 - start));
sort.printValue("sort-result.txt");
long end_2 = System.currentTimeMillis();
System.out.println("writer file time: " + (end_2 - end_1));
}
}