关于读取txt文件的问题。

[wsyccc0725]

要把txt文件中的字母abcdefghijklm转换成nopqrstuvwxyz。code 写出来了，但是为什么printout的只有最后一行。

import java.util.*;
import java.io.*;
public class Rot {

/**
* @param args
*/
public static void main(String[] args)throws IOException {
// TODO Auto-generated method stub
String FileName=readFileName("Please enter an input file name:");
Scanner infile = new Scanner (new File(FileName+".txt"));
String result=transformed(infile);
FileName=readFileName("Please enter an output file name:");
PrintWriter outfile=new PrintWriter(new FileWriter(FileName+".txt"));
System.out.println(result);
outfile.println(result);
infile.close();
outfile.close();
}
public static String readFileName(String msg){
Scanner inkey = new Scanner(System.in);
System.out.println(msg);
return inkey.nextLine();
}
public static String transformed(Scanner in)throws IOException{
String line=null;
int num=13;
while(in.hasNextLine()){
line=in.nextLine();
int count=0;
while(count<line.length()){
char letter=line.charAt(count);
if(letter>='a' && letter<'n')
letter+=num;
else if(letter>='n' && letter<='z')
letter-=num;
if(letter>='A' && letter<'N')
letter+=num;
else if(letter>='N' && letter<='Z')
letter-=num;
count++;
}
}
return line;
}
}

[wsyccc0725]

[Quote=引用 1 楼 cl61917380 的回复:]

这就要用到传说中的IO流了。
Java code

public static void main(String[] args) throws IOException {
String dir = "D:/workspace/TestProject/src/com/io/ByteReadFileTest.java";
String src = "D:/work……
[/Quote]
这个我们还没有学到，老师只教了怎么用Scanner读取和写出txt文件。麻烦您帮我看看这个程序有什么错么？

import java.util.*;
import java.io.*;
public class Rot {

	/**
	 * @param args
	 */
	public static void main(String[] args)throws IOException {
		// TODO Auto-generated method stub
		String FileName=readFileName("Please enter an input file name:");
		Scanner infile = new Scanner (new File(FileName+".txt"));
		String result=transformed(infile);
		FileName=readFileName("Please enter an output file name:");
		PrintWriter outfile=new PrintWriter(new FileWriter(FileName+".txt"));
		System.out.println(result);
		outfile.println(result);
		infile.close();
		outfile.close();
	}
	public static String readFileName(String msg){
		Scanner inkey = new Scanner(System.in);
		System.out.println(msg);
		return inkey.nextLine();
	}
	public static String transformed(Scanner in)throws IOException{
		String line=null;
		int num=13;
		while(in.hasNextLine()){
			line=in.nextLine();
			int count=0;
			while(count<line.length()){
				char letter=line.charAt(count);
				if(letter>='a' && letter<'n')
					letter+=num;
				else if(letter>='n' && letter<='z')
					letter-=num;
				if(letter>='A' && letter<'N')
					letter+=num;
				else if(letter>='N' && letter<='Z')
					letter-=num;
				count++;
			}
		}
		return line;
	}
}

[qybao]

while(in.hasNextLine()){ //你每次循环读入一行，进行转换，
line=in.nextLine(); //下一次循环的时候，前一行的信息就丢失了

所以，你应该把每次循环的结果保存到一个临时变量，最后把所有结果返回

即

StringBuilder buf = new StringBuilder();
while(in.hasNextLine()){
    line=in.nextLine();
    int count=0;
    while(count<line.length()){
        char letter=line.charAt(count);
        if(letter>='a' && letter<'n')
            letter+=num;
        else if(letter>='n' && letter<='z')
            letter-=num;
        if(letter>='A' && letter<'N')
            letter+=num;
        else if(letter>='N' && letter<='Z')
            letter-=num;
        count++;
        buf.append(letter); //保留到临时变量
    }
    buf.append("\n"); //追加换行符
}
return buf.toString();

[coooliang]

这就要用到传说中的IO流了。

public static void main(String[] args) throws IOException {
		String dir = "D:/workspace/TestProject/src/com/io/ByteReadFileTest.java";
		String src = "D:/workspace/TestProject/src/com/io/out.java";
		InputStream input = new FileInputStream(dir);
		OutputStream out = new FileOutputStream(src);
		int length = 0;
		byte[] b = new byte[1024];// 缓冲区
		while ((length = input.read(b)) != -1) {
			System.out.print(new String(b, 0, length));
			out.write(b, 0, length);// 重要...
			out.flush();
		}
		out.close();
	}