1.將控制檯輸入的寫入到txt檔案中

package com.soulant.main;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
/*將控制檯輸入的字元-轉化成位元組-再轉化為字元流寫入檔案
注意事項:
 "E:\\JavaTest\\HelloWorld.txt" 而不是  "E:\JavaTest\HelloWorld.txt"
      將字串進行轉義
*/
 

public class TestIo {

    public static void main(String[] args)throws IOException {
        BufferedReader in  = new BufferedReader(new InputStreamReader(System.in));
        String s;

        try {
            while ((s = in.readLine()).length()!=0) {
                System.out.println(s);
                PrintWriter out
 
 = new PrintWriter(new BufferedWriter(new FileWriter("E:\\JavaTest\\HelloWorld.txt")));
                out.println(s);
                System.out.println("寫入");
                out.close();
            }
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace
 
();
        }


    }

}

將txt檔案裡面的內容寫入到另一個檔案中

package com.soulant.main;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
/*
 * 將一個txt檔案裡面的內容寫入到另一個txt檔案
 * 
 */
public class TestFile {

    public static void main(String[] args) {
        File filein,fileout;
        BufferedReader bf = null;
        PrintWriter pw = null;
        filein = new File("E:\\JavaTest\\filein.txt");
        fileout = new File("E:\\JavaTest\\fileout.txt");//如果沒有就會自動建立
        try {
            bf = new BufferedReader(new FileReader(filein));
            pw = new PrintWriter(fileout);//PrintWriter為列印流，也可以使用BufferedWriter.
            String line = bf.readLine();
            while (line!=null) {
            pw.println(line);
            line = bf.readLine();

            }
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally{

                try {
                    if (bf!=null) {
                    bf.close();
                    bf = null;
                    }
                    if (pw!=null) {
                        pw.close();
                        pw = null;
                        }
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();


            }
        }
    }

}