java 向文件写入，从文件读出

import java.io.*;

public class Test {

public static void main(String[] args){
String s = new String();
String s1 = new String();
try {

BufferedWriter output = new BufferedWriter(new FileWriter("E:\\123.txt")); //写入流
output.write(s1); //s1为写入的字符串
output.close();

BufferedReader input = new BufferedReader(new FileReader("E:\\123.txt")); //读取流

while((s = input.readLine())!=null){ //判断是否读到了最后一行
System.out.println(s);
}

input.close();

} catch (Exception e) {

}
}

}

import java.io.*;
public class IO3
{
public static void main(String args[])
{
String str[]={"First line\n","Second line\n","Last line\n"};
try
{
RandomAccessFile rf=new RandomAccessFile

("demo.txt"