Java對TXT文件的操做(建立、讀取、複製)

運行效果：

代碼：

package com.io;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.util.Arrays;
import java.util.Scanner;
import java.util.Vector;

public class CreateAndReadTxt {
	// 文件名稱
	public static String fileName = ".txt";
	public static String newFileName = ".txt";
	// 文件路徑
	public final static String URL = System.getProperty("user.dir");

	// CreateAndReadTxt.class.getResource("/").getPath();

	// 建立TXT文件
	public static void createTxtFile(String fName, String fileContent) {
		// 建立文件
		fileName = fName + fileName;
		File file = new File(fileName);
		// 能夠更改
		file.setWritable(true);
		// 判斷當前路徑下是否存在同名文件
		boolean isExist = file.exists();
		if (isExist) {
			// 文件存在，刪除
			file.delete();
		}
		// 寫入文件
		try {
			// 文件寫入對象
			FileOutputStream fos = new FileOutputStream(file);
			// 輸入流寫入----默認字符爲GBK
			OutputStreamWriter osw = new OutputStreamWriter(fos);
			// 寫入
			osw.write(fileContent);
			// 寫入完畢後關閉
			osw.close();
			System.out.println("成功建立文件:\t"+fileName);
		} catch (IOException e) {
			System.out.println("寫入文件失敗:\t" + e.getMessage());
		}
	}

	// 閱讀文件
	public static void readFile(String fileName) {
		System.out.println("開始讀取文件:\t" + fileName);
		// 產生文件對象
		File file = new File(fileName);
		//
		try {
			// 字符讀取
			FileReader fr = new FileReader(file);
			// 緩衝處理
			BufferedReader br = new BufferedReader(fr);
			String str = "";
			while ((str = br.readLine()) != null) {
				System.out.println(str);
			}
			// 關閉
			br.close();
			fr.close();
		} catch (FileNotFoundException e) {
			System.out.println("讀取文件失敗:\t" + e.getMessage());
		} catch (IOException e) {
			System.out.println("讀取文件失敗:\t" + e.getMessage());
		}
	}
	// 文件複製
	public static void copyFile(String fromFileName,String toFileName){
		//讀取文件
		File file = new File(fromFileName);
		try {
			FileReader fr = new FileReader(file);
			BufferedReader br = new BufferedReader(fr);
			// 定義接收變量
			Vector<Double> vec = new Vector<Double>();
			String s = "";
			while(null!=(s=br.readLine())){
				vec.add(Double.parseDouble(s));
			}
			br.close();
			fr.close();
			// 保存到數組並進行排序
			Double dou[] = new Double[vec.size()];
			vec.toArray(dou);
			Arrays.sort(dou);
			System.out.println("========複製文件=========");
			// 寫入新文件
			newFileName = "副本"+newFileName;
			File newFile = new File(toFileName);
			FileOutputStream fos = new FileOutputStream(newFile, true);
			OutputStreamWriter osm = new OutputStreamWriter(fos);
			for(Double d:dou){
				osm.write(d.doubleValue()+"\n");
			}
			osm.close();
			fos.close();
		} catch (FileNotFoundException e) {
			System.out.println("讀取文件失敗:\t" + e.getMessage());
		} catch (IOException e) {
			System.out.println("讀取文件失敗:\t" + e.getMessage());
		}
		
	}
	public static void main(String[] args) {
		/**
		 * 構造數據
		 */
		Scanner scan = new Scanner(System.in);
		StringBuilder sb = new StringBuilder();
		String s = "";
		while(!("end".equals(s = scan.next()))){// 當輸入end時，結束
			sb.append(s);
			sb.append("\n");
		}
		scan.close();
		/**
		 * 使用數據
		 */
		CreateAndReadTxt.createTxtFile("creat", sb.toString());
		CreateAndReadTxt.readFile(fileName);
		System.out.println(fileName);
		CreateAndReadTxt.copyFile(fileName, newFileName);
		CreateAndReadTxt.readFile(newFileName);
	}

}