去掉重複值IO操作

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;

public class IoTest {

	private static final String DIR_PATH = "C:\\新建文件夾";
	private static final String WRITE_FILE_PATH = "C:\\新建文件夾\\output\\test.txt";
	private static int readFileCount = 0;

	public static void main(String[] args) {
		Set<String> userIdSet = new LinkedHashSet<String>();
		List<String> filePathList = getFileNames(DIR_PATH);
		for (String filePath : filePathList) {
			readFile(filePath, userIdSet);
		}
		writeFile(WRITE_FILE_PATH, userIdSet);
	}

	private static void writeFile(String writeFilePath, Set<String> userIdSet) {
		File dir = new File(writeFilePath.substring(0, writeFilePath
				.lastIndexOf("\\")));
		if (!dir.exists()) {
			dir.mkdirs();
		}
		File file = new File(writeFilePath);
		if (!file.exists()) {
			try {
				file.createNewFile();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}

		FileWriter fileWriter = null;
		BufferedWriter bufferedWriter = null;
		try {
			fileWriter = new FileWriter(writeFilePath, false);// 第二個參數表示：是否爲追加模式
			bufferedWriter = new BufferedWriter(fileWriter);
			int writeFileCount = 0;
			for (Object userId : userIdSet) {
				bufferedWriter.write(userId.toString());
				bufferedWriter.newLine();
				System.out.println(++writeFileCount + " : " + userId.toString()
						+ " write");
			}
			bufferedWriter.write("=====end=====");
			bufferedWriter.flush();
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			try {
				if (bufferedWriter != null) {
					bufferedWriter.close();
				}
				if (fileWriter != null) {
					fileWriter.close();
				}
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}

	private static void readFile(String readFilePath, Set<String> userIdSet) {
		String userId;
		FileReader fileReader = null;
		BufferedReader bufferedReader = null;
		try {
			fileReader = new FileReader(readFilePath);
			bufferedReader = new BufferedReader(fileReader);
			while ((userId = bufferedReader.readLine()) != null) {
				userIdSet.add(userId);
				System.out.println(++readFileCount + " : " + userId + " read");
			}
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			try {
				if (bufferedReader != null) {
					bufferedReader.close();
				}
				if (fileReader != null) {
					fileReader.close();
				}
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}

	/**
	 * 獲得目錄下所有文件完整路徑
	 * @param dirPath 目錄路徑
	 * @return
	 */
	private static List<String> getFileNames(String dirPath) {
		List<String> filePathList = new ArrayList<String>();
		File rootFile = new File(dirPath);
		String[] nameArray = rootFile.list();
		for (int i = 0; i < nameArray.length; i++) {
			File tempFile = new File(rootFile.getPath(), nameArray[i]);
			if (tempFile.isFile()) {
				filePathList.add(dirPath + "\\" + nameArray[i]);
			}
		}
		return filePathList;
	}
}